Basic knowledge of Python variables
- 2021-12-09 09:14:29
- OfStack
1. What are variables
The so-called variable refers to the amount whose value can be changed during the running of a program.
Example: In mathematics
x
And
y
Is the variable,
Python
The difference in is that variables don't just store numbers, they can store values of any data type.
2. Variable naming rules
Variable names can only include letters, numbers and underscores Numbers cannot be used for 1 character Variable names are case sensitive Keywords and reserved words cannot be used
3. Keywords and reserved words in python
Keyword: Yes
Pyt
Some words in hon have been given specific meanings, which requires developers not to use these keywords as identifiers to name variables, functions, classes, templates and other objects when developing programs.
Reserved word: The system is retained (it may never be used, but you can't use it).
Get keywords and reserved words:
import keyword
print(keyword.kwlist)
4. Common variable names
Examples:
Type 1:myName myFriendName
Type 2:
MyName MyFriendName
Type 2:
my_name my_friend_name
5. Assignment of variables
Python
It is a dynamic programming language. In the process of program execution, variables can be given different types of values, and the data types of variables can be changed at the same time.
The assignment of variables does not require type declaration,
Python
Variable types are automatically declared.
Assignment operator
“=”
Used to assign values to variables.
Examples:
a = 0.01
b = 666
c = " Hello, Wrold"
print(a)
print(b)
print(c)
print(a,b,c)
Multivariable assignment
a = 1
b = 1
c = 1
print(a,b,c)
# Code equivalent to
a = b = c = 1
print(a,b,c)
a = 1
b = 2.2
c = "HelloWorld"
d = True
print(a,b,c,d)
# Code equivalent to
a , b ,c ,d = 1 , 2.2 ,"HelloWorld" , True
print(a,b,c,d)
6. Data Type of Variable
Python
The data types of include numbers, Booleans, strings, tuples, lists, dictionaries, and so on.
6.1. Figures
Numeric data types are used to store numeric values, including the following three types:
a.int
(Integer) is commonly referred to as an integer,
b.float
(Floating-point), also known as floating-point numbers, consists of integers and decimals.
c.complex
(Complex) Consists of a real number and a complex number; The general form is x + yj.
6.2. Boolean Types
bool
(Boolean) is a rather special type that has only
True
(True) and
False
(False) Two values (pay attention to case)
6.3. String
str
(String) is arbitrary text enclosed in single or double quotation marks, such as
' abc '
,
" abc "
Escape characters are defined as
Python
0
Start, followed by 1 character, for example:
Python
1
Python
It also allows r before single quotation marks to indicate that strings inside single quotation marks are not escaped by default
6.4. type () Function
Function: Returns the type of object
a = 0.01
print(type(a))