Data Types and Operators

Arithmetic operators

+ Addition
- Subtraction
* Multiplication
/ Division
% Mod (the remainder after dividing)
** Exponentiation (note that ^ does not do this operation, as you might have seen in other languages)
// Divides and rounds down to the nearest integer

Variables

Assign value

the following two are equivalent in terms of assignment

x = 3
y = 4
z = 5

and

x, y, z = 3, 4, 5

Reserved world in python

Pythonic way to name variables

YES

my_height = 58
my_lat = 40
my_long = 105

my height = 58
MYLONG = 40
MyLat = 105

Varaibles and Assignment operator

a = 10
a = a + 10 -6

or

a  += 10 - 6

Scientific notation

4.445e8 is equal to 4.445 * 10 ** 8 which is equal to 444500000.0.

Integers and Floats

浮点数创建直接在后面加上一个点就行

>>> print(10.)
10.0

或者

x = int(4.7)   # x is now an integer 4
y = float(4)   # y is now a float of 4.0

type function

查看是什么类型的

>>> print(type(10))

>>> print(type(10.0))

>>> print(type(int(10.0)))

>>> print(type(float(10)))

Floating Issues

>>> 0.1+0.1+0.1
0.30000000000000004

>>> print(.1 + .1 + .1 == .3)
False

Floating Point Arithmetic: Issues and Limitations小数部分不能完全表示为二进制分数

Boolean Comparison and Logical Operators

Strings

Strings in Python are shown as the variable type str. You can define a string with either double quotes " or single quotes '

>>> my_string = 'this is a string!'
>>> my_string2 = "this is also a string!!!"

operators of strings

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len() function

len() is a built-in Python function that returns the length of an object, like a string. The length of a string is the number of characters in the string. This will always be an integer.

change type

such as

>>> age="22"
>>> print(int(age))
22
>>> print(type(int(age)))

String Methods

No professional has all the methods memorized, which is why understanding how to use documentation and find answers is so important. Gaining a strong grasp of the foundations of programming will allow you to use those foundations to use documentation to build so much more than someone who tries to memorize all the built-in methods in Python. (学会使用文档，而不是记住所有的这些方法)

You will find that the string method documentation is one of the most valuable resources for writing code, and not only when it comes to strings or writing code in Python!

Important string method

format()

》maria_string = "Maria loves {} and {}"
》print(maria_string.format("math","statistics"))

》Maria loves math and statistics

split()

string split document
This function or method returns a data container called a list that contains the words from the input string.

>>> '1,2,3'.split(',')
['1', '2', '3']

python code Style

PEP 8 -- Style Guide for Python Code

Whitespace

合理利用空格来编写清晰可读的代码

References

Python Tutorial

Thanks Instructor

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