1. Basic use of variables
1.1 Definition and assignment of variables
Python is a dynamic language, so there is no need to specify the data type of the variable when defining the variable.
Variable name=value
qq_number = "12345"
price = 10
2. Basic data types
The basic data types of python are as follows:
-
Integer type (int): 3
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Long (long): 32344343242424
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Boolean type (boolean): True/False
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Floating point type (float): 1.23
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Complex type (complex): Mainly used for scientific calculations, such as fluctuation problems, capacitance and inductance problems, and calculus problems
3. Variable composition and its rules
3.1 identifier
Namely variable names, function names, etc.
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Identifier consists of letters, underscores, and numbers
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Cannot start with a number
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Cannot be a keyword
3.2 Keywords
An identifier that has been defined or used within Python.
View keywords:
import keyword
print(keyword).kwlist）
The keywords are as follows:
| False | assert | continue | except | if | nonlocal |
|---|---|---|---|---|---|
| True | await | def | finally | import | not |
| None | break | of the | for | in | or |
| and | async | elif | from | is | pass |
| as | class | else | global | lambda | raise |
| return | try | while | with | yield |
3.3 Naming rules
Identifiers are case sensitive and should be highly readable.
(1) Underscore style: first_name
(2) Camelback: FirstName
4. Variable input and output
4.1 Input
Input from the outside: input ("input prompt sentence")
>>>a = input("请输入金额：")
请输入金额：12
>>>a
'12'
Note that the content of input is a string type by default
4.2 Output
Through the print() function:
print(qq_number)
print(price)
4.3 Type conversion
| function | Description |
|---|---|
| int（x） | Convert X to integer |
| float（x） | Convert x to floating point |
Such as:
price =input("请输入苹果单价：")
weight=input("请输入苹果质量：")
#将字符串形式转换成小数形式
price=float(price)
weight=float(weight)
money=price*weight
print(money)
Note: The variables before and after conversion are not the same variable!
Improve:
price=float( input(“请输入苹果的单价：”) )
Weight=float(input(“请输入苹果的重量：”) )
Money=price*weight
Print(money)
4.4 Formatted output of variables
(% is a formatting character)
| Formatting character | meaning |
|---|---|
| %s | String |
| %f | Floating point number, %0.2f, %06f |
| %d | Integer |
format:
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print("text description %s"% variable name)
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print("text description %s %s"% (variable name, variable name))
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%06f description: a total of 6 bits of data, add 0 to the left when less than 6 bits; more than 6 bits will be output in the original position
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%6d Description: A total of 6 bits of data, if less than 6 bits, add a space on the left; more than 6 bits will be output in the original position
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%.2f Description: The output format is two digits after the decimal point (rounded)