Python的if语句
概述
Python支持的常用数据逻辑判断条件
等于 :a == b
不等于 :a != b
小于 :a < b
小于等于 :a <= b
大于 :a > b
大于等于 :a >= b
if语句
a = 66
b = 200
if b > a :
print("b is greater than a")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
b is greater than a
Process finished with exit code 0
if…elif语句
a = 200
b = 200
if b > a :
print("b is greater than a")
elif b == a:
print("b is equal a")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
b is equal a
Process finished with exit code 0
if…elif…else语句
a = 200
b = 99
if b > a :
print("b is greater than a")
elif b == a:
print("b is equal a")
else:
print("b is less than a")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
b is less than a
Process finished with exit code 0
Python 依赖缩进,使用空格来定义代码中的范围。其他编程语言通常使用花括号来实现此目的
单行if语句
如果只有一条语句要执行,则可以将其与 if 语句放在同一行。
a = 200
b = 66
if a > b: print("a is greater than b")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
a is greater than b
Process finished with exit code 0
单行if…else语句
如果只有两条语句要执行,一条用于 if,另一条用于 else,则可以将它们全部放在同一行
a = 200
b = 66
print("A") if a > b else print("B")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
A
Process finished with exit code 0
有三个条件的单行if…else语句
a = 200
b = 66
print("A") if a > b else print("=") if a == b else print("B")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
A
Process finished with exit code 0
组合条件的if语句
and if语句
a = 200
b = 66
c = 500
if a > b and c > a:
print("Both conditions are True")
else:
print("conditions is not True")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
Both conditions are True
Process finished with exit code 0
or if语句
a = 200
b = 66
c = 500
if a > b or a > c:
print("At least one of the conditions is True")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
At least one of the conditions is True
Process finished with exit code 0
嵌套if语句
x = 52
if x > 10:
print("Above ten,")
if x > 20:
print("and also above 20!")
else:
print("but not above 20.")
输出:
E:\Python3\Exercise\venv\Scripts\python.exe E:/Python3/Exercise/venv/01.py
Above ten,
and also above 20!
Process finished with exit code 0
pass语句
if 语句不能为空,但是如果您处于某种原因写了无内容的 if 语句,请使用 pass 语句来避免错误。
a = 66
b = 200
if b > a:
pass