Python 2.X 与 3.X 版本的重要区别
最近接触了Python后，看一些源代码的时候发现编译器会对一些正确的代码报错。原因就在于版本的问题。
那么这里收集了很多网络上的区别，分享给大家。
再次感谢原文的作者：
http://blog.jobbole.com/
__future__模块
[回到目录]
Python 3.x引入了一些与Python 2不兼容的关键字和特性，在Python 2中，可以通过内置的__future__模块导入这些新内容。如果你希望在Python 2环境下写的代码也可以在Python 3.x中运行，那么建议使用__future__模块。例如，如果希望在Python 2中拥有Python 3.x的整数除法行为，可以通过下面的语句导入相应的模块。
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
from
__future__
import
division
|
下表列出了__future__中其他可导入的特性：
| 特性 | 可选版本 | 强制版本 | 效果 |
|---|---|---|---|
| nested_scopes | 2.1.0b1 | 2.2 | PEP 227: Statically Nested Scopes |
| generators | 2.2.0a1 | 2.3 | PEP 255: Simple Generators |
| division | 2.2.0a2 | 3.0 | PEP 238: Changing the Division Operator |
| absolute_import | 2.5.0a1 | 3.0 | PEP 328: Imports: Multi-Line and Absolute/Relative |
| with_statement | 2.5.0a1 | 2.6 | PEP 343: The “with” Statement |
| print_function | 2.6.0a2 | 3.0 | PEP 3105: Make print a function |
| unicode_literals | 2.6.0a2 | 3.0 | PEP 3112: Bytes literals in Python 3000 |
（来源： https://docs.python.org/2/library/future.html)
示例：
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
from
platform
import
python_version
|
print函数
[回到目录]
虽然print语法是Python 3中一个很小的改动，且应该已经广为人知，但依然值得提一下：Python 2中的print语句被Python 3中的print()函数取代，这意味着在Python 3中必须用括号将需要输出的对象括起来。
在Python 2中使用额外的括号也是可以的。但反过来在Python 3中想以Python2的形式不带括号调用print函数时，会触发SyntaxError。
Python 2
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 88.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
|
print
'Python'
,
python_version
(
)
print
'Hello, World!'
print
(
'Hello, World!'
)
print
"text"
,
;
print
'print more text on the same line'
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 88.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
|
Python
2.7.6
Hello
,
World
!
Hello
,
World
!
text
print
more
text
on
the
same
line
|
Python 3
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
print
(
'Python'
,
python_version
(
)
)
print
(
'Hello, World!'
)
print
(
"some text,"
,
end
=
""
)
print
(
' print more text on the same line'
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 73.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
|
Python
3.4.1
Hello
,
World
!
some
text
,
print
more
text
on
the
same
line
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
'Hello, World!'
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 88.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
|
File
"<ipython-input-3-139a7c5835bd>"
,
line
1
print
'Hello, World!'
^
SyntaxError
:
invalid
syntax
|
注意：
在Python中，带不带括号输出”Hello World”都很正常。但如果在圆括号中同时输出多个对象时，就会创建一个元组，这是因为在Python 2中，print是一个语句，而不是函数调用。
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 73.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
|
print
'Python'
,
python_version
(
)
print
(
'a'
,
'b'
)
print
'a'
,
'b'
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 73.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
|
Python
2.7.7
(
&
#039;a', 'b')
a
b
|
整数除法
[回到目录]
由于人们常常会忽视Python 3在整数除法上的改动（写错了也不会触发Syntax Error），所以在移植代码或在Python 2中执行Python 3的代码时，需要特别注意这个改动。
所以，我还是会在Python 3的脚本中尝试用float(3)/2或 3/2.0代替3/2，以此来避免代码在Python 2环境下可能导致的错误（或与之相反，在Python 2脚本中用from __future__ import division来使用Python 3的除法）。
Python 2
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
print
'Python'
,
python_version
(
)
print
'3 / 2 ='
,
3
/
2
print
'3 // 2 ='
,
3
/
/
2
print
'3 / 2.0 ='
,
3
/
2.0
print
'3 // 2.0 ='
,
3
/
/
2.0
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
Python
2.7.6
3
/
2
=
1
3
// 2 = 1
3
/
2.0
=
1.5
3
// 2.0 = 1.0
|
Python 3
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
print
(
'Python'
,
python_version
(
)
)
print
(
'3 / 2 ='
,
3
/
2
)
print
(
'3 // 2 ='
,
3
/
/
2
)
print
(
'3 / 2.0 ='
,
3
/
2.0
)
print
(
'3 // 2.0 ='
,
3
/
/
2.0
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
Python
3.4.1
3
/
2
=
1.5
3
// 2 = 1
3
/
2.0
=
1.5
3
// 2.0 = 1.0
|
Unicode
[回到目录]
Python 2有基于ASCII的str()类型，其可通过单独的unicode()函数转成unicode类型，但没有byte类型。
而在Python 3中，终于有了Unicode（utf-8）字符串，以及两个字节类：bytes和bytearrays。
Python 2
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
'Python'
,
python_version
(
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
Python
2.7.6
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
type
(
unicode
(
'this is like a python3 str type'
)
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
&
lt
;
type
&
#039;unicode'>
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
type
(
b
'byte type does not exist'
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
&
lt
;
type
&
#039;str'>
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
'they are really'
+
b
' the same'
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
they
are
really
the
same
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
type
(
bytearray
(
b
'bytearray oddly does exist though'
)
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
&
lt
;
type
&
#039;bytearray'>
|
Python 3
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'Python'
,
python_version
(
)
)
print
(
'strings are now utf-8 u03BCnicou0394é!'
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
Python
3.4.1
strings
are
now
utf
-
8
μ
nicoΔé
!
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'Python'
,
python_version
(
)
,
end
=
""
)
print
(
' has'
,
type
(
b
' bytes for storing data'
)
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
Python
3.4.1
has
&
lt
;
class
&
#039;bytes'>
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'and Python'
,
python_version
(
)
,
end
=
""
)
print
(
' also has'
,
type
(
bytearray
(
b
'bytearrays'
)
)
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
and
Python
3.4.1
also
has
&
lt
;
class
&
#039;bytearray'>
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
'note that we cannot add a string'
+
b
'bytes for data'
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 124.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
|
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
-
TypeError
Traceback
(
most
recent
call
last
)
&
lt
;
ipython
-
input
-
13
-
d3e8942ccf81
&
gt
;
in
&
lt
;
module
&
gt
;
(
)
--
--
&
gt
;
1
&
#039;note that we cannot add a string' + b'bytes for data'
TypeError
:
Can
&
#039;t convert 'bytes' object to str implicitly
|
xrange
[回到目录]
在Python 2.x中，经常会用xrange()创建一个可迭代对象，通常出现在“for循环”或“列表/集合/字典推导式”中。
这种行为与生成器非常相似（如”惰性求值“），但这里的xrange-iterable无尽的，意味着可能在这个xrange上无限迭代。
由于xrange的“惰性求知“特性，如果只需迭代一次（如for循环中），range()通常比xrange()快一些。不过不建议在多次迭代中使用range()，因为range()每次都会在内存中重新生成一个列表。
在Python 3中，range()的实现方式与xrange()函数相同，所以就不存在专用的xrange()（在Python 3中使用xrange()会触发NameError）。
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 178.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
8
9
10
|
import
timeit
n
=
10000
def
test_range
(
n
)
:
return
for
i
in
range
(
n
)
:
pass
def
test_xrange
(
n
)
:
for
i
in
xrange
(
n
)
:
pass
|
Python 2
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 148.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
8
|
print
'Python'
,
python_version
(
)
print
'ntiming range()'
%
timeit
test_range
(
n
)
print
'nntiming xrange()'
%
timeit
test_xrange
(
n
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 133.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
|
Python
2.7.6
timing
range
(
)
1000
loops
,
best
of
3
:
433
µ
s
per
loop
timing
xrange
(
)
1000
loops
,
best
of
3
:
350
µ
s
per
loop
|
Python 3
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 88.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
|
print
(
'Python'
,
python_version
(
)
)
print
(
'ntiming range()'
)
%
timeit
test_range
(
n
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 88.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
|
Python
3.4.1
timing
range
(
)
1000
loops
,
best
of
3
:
520
µ
s
per
loop
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 43.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
|
print
(
xrange
(
10
)
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 124.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
|
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
-
NameError
Traceback
(
most
recent
call
last
)
in
(
)
--
--
&
gt
;
1
print
(
xrange
(
10
)
)
NameError
:
name
&
#039;xrange' is not defined
|
Python 3中的range对象中的__contains__方法
另一个值得一提的是，在Python 3.x中，range有了一个新的__contains__方法。__contains__方法可以有效的加快Python 3.x中整数和布尔型的“查找”速度。
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 223.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
8
9
10
11
12
13
|
x
=
10000000
def
val_in_range
(
x
,
val
)
:
return
val
in
range
(
x
)
def
val_in_xrange
(
x
,
val
)
:
return
val
in
xrange
(
x
)
print
(
'Python'
,
python_version
(
)
)
assert
(
val_in_range
(
x
,
x
/
2
)
==
True
)
assert
(
val_in_range
(
x
,
x
/
/
2
)
==
True
)
%
timeit
val_in_range
(
x
,
x
/
2
)
%
timeit
val_in_range
(
x
,
x
/
/
2
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 73.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
|
Python
3.4.1
1
loops
,
best
of
3
:
742
ms
per
loop
1000000
loops
,
best
of
3
:
1.19
µ
s
per
loop
|
根据上面的timeit的结果，查找整数比查找浮点数要快大约6万倍。但由于Python 2.x中的range或xrange没有__contains__方法，所以在Python 2中的整数和浮点数的查找速度差别不大。
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 223.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
8
9
10
11
12
13
|
print
'Python'
,
python_version
(
)
assert
(
val_in_xrange
(
x
,
x
/
2.0
)
==
True
)
assert
(
val_in_xrange
(
x
,
x
/
2
)
==
True
)
assert
(
val_in_range
(
x
,
x
/
2
)
==
True
)
assert
(
val_in_range
(
x
,
x
/
/
2
)
==
True
)
%
timeit
val_in_xrange
(
x
,
x
/
2.0
)
%
timeit
val_in_xrange
(
x
,
x
/
2
)
%
timeit
val_in_range
(
x
,
x
/
2.0
)
%
timeit
val_in_range
(
x
,
x
/
2
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
Python
2.7.7
1
loops
,
best
of
3
:
285
ms
per
loop
1
loops
,
best
of
3
:
179
ms
per
loop
1
loops
,
best
of
3
:
658
ms
per
loop
1
loops
,
best
of
3
:
556
ms
per
loop
|
下面的代码证明了Python 2.x中没有__contain__方法：
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'Python'
,
python_version
(
)
)
range
.
__contains__
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
Python
3.4.1
&
lt
;
slot
wrapper
&
#039;__contains__' of 'range' objects
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'Python'
,
python_version
(
)
)
range
.
__contains__
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 154.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
8
|
Python
2.7.7
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
-
AttributeError
Traceback
(
most
recent
call
last
)
&
lt
;
ipython
-
input
-
7
-
05327350dafb
&
gt
;
in
&
lt
;
module
&
gt
;
(
)
1
print
&
#039;Python', python_version()
--
--
&
gt
;
2
range
.
__contains__
AttributeError
:
&
#039;builtin_function_or_method' object has no attribute '__contains__'
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'Python'
,
python_version
(
)
)
xrange
.
__contains__
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 169.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
6
7
8
9
|
Python
2.7.7
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
-
AttributeError
Traceback
(
most
recent
call
last
)
in
(
)
1
print
&
#039;Python', python_version()
--
--
&
gt
;
2
xrange
.
__contains__
AttributeError
:
type
object
&
#039;xrange' has no attribute '__contains__'
|
关于Python 2中xrange()与Python 3中range()之间的速度差异的一点说明：
有读者指出了Python 3中的range()和Python 2中xrange()执行速度有差异。由于这两者的实现方式相同，因此理论上执行速度应该也是相同的。这里的速度差别仅仅是因为Python 3的总体速度就比Python 2慢。
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 103.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
5
|
def
test_while
(
)
:
i
=
0
while
i
<
20000
:
i
+=
1
return
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
(
'Python'
,
python_version
(
)
)
%
timeit
test_while
(
)
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 88.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
3
4
|
Python
3.4.1
%
timeit
test_while
(
)
100
loops
,
best
of
3
:
2.68
ms
per
loop
|
<textarea wrap="soft" class="crayon-plain print-no" data-settings="dblclick" readonly="readonly" style="border: none; outline: none; display: block; -webkit-appearance: none; padding-top: 0px; padding-right: 5px; padding-left: 5px; width: 608px; height: 58.5px; resize: none; overflow: auto; margin: 0px; position: absolute; opacity: 0; border-radius: 0px; box-shadow: none; white-space: pre; word-wrap: normal; color: rgb(0, 0, 0); tab-size: 4; z-index: 0; font-size: 13px !important; line-height: 15px !important; font-family: Monaco, MonacoRegular, 'Courier New', monospace !important; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></textarea>
|
1
2
|
print
'Python'
,
python_version
(
)
%
timeit
test_while
(
)
|