python笔记1

使用工具

本文使用的是jupyter notebook 这一工具

如何配置jupyter notebook

个人建议直接使用anaconda 会自动配置好环境，对于初学者来说也是非常大方便。网址如下，根据自己计算机在网页的最下端下载相应的版本。
anaconda下载链接

如何配置jupyter notebook环境

下载后jupyter notebook打开即可

我们可以在右上角出选择创建python

python的小功能

查看python的版本

通过下面的代码你就可以查看python的版本

import sys
sys.version

python介绍

python 是一种面向对象的解释形语言，通过jupyter notebook我们可以简单的得到一些结果如下：

print('hello world!')

hello world!

python中的帮助

python作为现在最流行的计算机语言，是因为其中的模块、包已经对象的类型十分多，所以我们不仅需要掌握python的基础语言，还需要掌握python中每个包的用法，下面几种方法就是我们常用的几种方法去查看一个包的帮助信息：

help(list)

主要用来查看函数、类、模块等的详细说明

Help on class list in module builtins:

class list(object)
 |  list(iterable=(), /)
 |  
 |  Built-in mutable sequence.
 |  
 |  If no argument is given, the constructor creates a new empty list.
 |  The argument must be an iterable if specified.
 |  
 |  Methods defined here:
 |  
 |  __add__(self, value, /)
 |      Return self+value.
 |  
 |  __contains__(self, key, /)
 |      Return key in self.
 |  
 |  __delitem__(self, key, /)
 |      Delete self[key].
 |  
 |  __eq__(self, value, /)
 |      Return self==value.
 |  
 |  __ge__(self, value, /)
 |      Return self>=value.
 |  
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |  
 |  __getitem__(...)
 |      x.__getitem__(y) <==> x[y]
 |  
 |  __gt__(self, value, /)
 |      Return self>value.
 |  
 |  __iadd__(self, value, /)
 |      Implement self+=value.
 |  
 |  __imul__(self, value, /)
 |      Implement self*=value.
 |  
 |  __init__(self, /, *args, **kwargs)
 |      Initialize self.  See help(type(self)) for accurate signature.
 |  
 |  __iter__(self, /)
 |      Implement iter(self).
 |  
 |  __le__(self, value, /)
 |      Return self<=value.
 |  
 |  __len__(self, /)
 |      Return len(self).
 |  
 |  __lt__(self, value, /)
 |      Return self<value.
 |  
 |  __mul__(self, value, /)
 |      Return self*value.
 |  
 |  __ne__(self, value, /)
 |      Return self!=value.
 |  
 |  __repr__(self, /)
 |      Return repr(self).
 |  
 |  __reversed__(self, /)
 |      Return a reverse iterator over the list.
 |  
 |  __rmul__(self, value, /)
 |      Return value*self.
 |  
 |  __setitem__(self, key, value, /)
 |      Set self[key] to value.
 |  
 |  __sizeof__(self, /)
 |      Return the size of the list in memory, in bytes.
 |  
 |  append(self, object, /)
 |      Append object to the end of the list.
 |  
 |  clear(self, /)
 |      Remove all items from list.
 |  
 |  copy(self, /)
 |      Return a shallow copy of the list.
 |  
 |  count(self, value, /)
 |      Return number of occurrences of value.
 |  
 |  extend(self, iterable, /)
 |      Extend list by appending elements from the iterable.
 |  
 |  index(self, value, start=0, stop=9223372036854775807, /)
 |      Return first index of value.
 |      
 |      Raises ValueError if the value is not present.
 |  
 |  insert(self, index, object, /)
 |      Insert object before index.
 |  
 |  pop(self, index=-1, /)
 |      Remove and return item at index (default last).
 |      
 |      Raises IndexError if list is empty or index is out of range.
 |  
 |  remove(self, value, /)
 |      Remove first occurrence of value.
 |      
 |      Raises ValueError if the value is not present.
 |  
 |  reverse(self, /)
 |      Reverse *IN PLACE*.
 |  
 |  sort(self, /, *, key=None, reverse=False)
 |      Sort the list in ascending order and return None.
 |      
 |      The sort is in-place (i.e. the list itself is modified) and stable (i.e. the
 |      order of two equal elements is maintained).
 |      
 |      If a key function is given, apply it once to each list item and sort them,
 |      ascending or descending, according to their function values.
 |      
 |      The reverse flag can be set to sort in descending order.
 |  
 |  ----------------------------------------------------------------------
 |  Static methods defined here:
 |  
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.
 |  
 |  ----------------------------------------------------------------------
 |  Data and other attributes defined here:
 |  
 |  __hash__ = None

dir(list)

主要用来查看对象的属性和方法

['__add__',
 '__class__',
 '__contains__',
 '__delattr__',
 '__delitem__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__getitem__',
 '__gt__',
 '__hash__',
 '__iadd__',
 '__imul__',
 '__init__',
 '__init_subclass__',
 '__iter__',
 '__le__',
 '__len__',
 '__lt__',
 '__mul__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__reversed__',
 '__rmul__',
 '__setattr__',
 '__setitem__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'append',
 'clear',
 'copy',
 'count',
 'extend',
 'index',
 'insert',
 'pop',
 'remove',
 'reverse',
 'sort']

关于面向对象的一些注意事项

当我们声明了一个对象如：

a=[1,2,3]#a是一个list
b=a
print(id(a),id(b),a is b)

140511890198144 140511890198144 True

可以看到结果是两个相同的id 这说明，a与b的存储位置相同，那么大家判断一下如果改变a，b是否会变：

a=[1,2,3]#a是一个list
b=a
a.append(5)#list的一个添加数字在末尾的方法
print(b)

[1, 2, 3, 5]

可以看出他们是同一个对象的引用，如果香让b单独为一个变量怎么办？一般我们都常用copy 包实现：

from copy import copy 
'''python 引用包的格式，一般为from ... import... 或者为 import ... as '''
a = [1,2,3,4,['boom','strange']]
b = copy(a)
a is b

False

此时如果我们改变第一维的list的a的时候b并不会变：

a.append(5)
print('a is :',a)
print('b is :',b)

这里是引用
a is : [1, 2, 3, 4, [‘boom’, ‘strange’], 5]
b is : [1, 2, 3, 4, [‘boom’, ‘strange’]]

但是如果我们改变第二维的list的时候，就会改变b：

a[4].append('shaklaka')
print(b)

[1, 2, 3, 4, [‘boom’, ‘strange’, ‘shaklaka’]]

所以这种方法我们通常称为浅拷贝，如果相让他完全不变，我们通常使用下面的方法，深拷贝:

from copy import deepcopy 
a = [1,2,3,4,['boom','strange']]
b = deepcopy(a)
a[4].append('shaklaka')
print(a)
print(b)

[1, 2, 3, 4, [‘boom’, ‘strange’, ‘shaklaka’]]
[1, 2, 3, 4, [‘boom’, ‘strange’]]