Python basics

Variables and types

In python, variables can be of any data type, which is represented by a variable name in the program
The variable name must be a combination of uppercase and lowercase English, numbers and underscores (_ ), and cannot start with a number, such as:

a=1 #Variable a is an integer
t007='T007” #Variable t007 is a string

When assigning values (such as a="ABC"), the Python interpreter does two things:

Create a string of'ABC' in memory
Create a variable named a in memory and point it to'ABC'

Identifiers and keywords##

What are keywords

Python some identifiers with special functions, these are the so-called keywords
The keyword is already used by python, so developers are not allowed to define the identifier with the same name as the keyword.

View keywords: enter python in the cmd window and enter the python command line

>>> import keyword #First introduce the keyword package
>>> keyword.kwlist #View keywords

Common keywords

and     as      assert    breakclasscontinue    def     del
elif    else    except    exec    finallyforfrom    global
ifinimport    is      lambda     not         or      pass
print   raise   returntrywhilewithyield

Output##

# Normal output
a=10print("This is the variable",a)

# Formatted output
age=20
name="Xiao Zhang"print("His age is%d years old"%age)print("his name is%s, nationality is%s"%(name,"China"))

operation result

Other output formats##

print("aaa","bbb","ccc")print("www","baidu","com",sep=".")

result:

print("hello",end="") #No line break
print("world",end="\t") #A tab before the next output
print("python",end="\n") #Wrap
print("end")

result:

enter##

password =input("Please enter password:") #keyboard input
print("The password you just entered is:",password)print("The types of numbers entered by the keyboard are:",type(password)) #The keyboard input is a string type

password_2 =int(password) #Cast to int type
print("The type after coercion is:",type(password_2))

result: