相等运算符（==）：用来判断二者是否“相等”，注意与赋值运算符（=）区分。
car = ‘audi‘ ‘‘‘在Python中判断是否相等时区分大小写‘‘‘ car == ‘Audi‘ ‘‘‘False‘‘‘ car.title() == ‘Audi‘ ‘‘‘True‘‘‘
（1）比较数字：小于(<)、小于等于(<=)、大于(>)、大于等于(>=)。
age = 19 age < 21 ‘‘‘True‘‘‘ age <= 21 ‘‘‘True‘‘‘ age > 19 ‘‘‘False‘‘‘ age >= 19 ‘‘‘True‘‘‘
（2）条件判断：不等于(!=)。
requested_topping = ‘mushrooms‘ if requested_topping != ‘anchovies‘: print( "Hold the anchovies!" )
使用逻辑运算符and和or可一次检查多个条件，形成更复杂的判断式。
age_0 = 22 age_1 = 18 age_0 >= 21 and age_1 >= 21 ‘‘‘False‘‘‘ age_0 >= 21 or age_1 >= 21 ‘‘‘True‘‘‘ age_1 = 22 age_0 >= 21 and age_1 >= 21 ‘‘‘True‘‘‘
上述程序中的判断语句，均可作为if语句的条件测试。若测试值为真，Python将会执行if语句所包含的代码，若为假则不会执行。
age = 19 if age >= 18: print( "You are old enough to vote!" )
age = 17 if age >= 18: print( "You are old enough to vote!" ) print( "Have you registered to vote yet?" ) else: print( "Sorry, you are too young to vote." ) print( "Please register to vote as soon as you turn 18!" )
输出为：
Sorry, you are too young to vote.
Please register to vote as soon as you turn 18!
和for语句相同，当测试值为真时，Python会执行所有紧跟在if语句之后且缩进的代码。
age = 12 if age < 4: price = 0 elif age < 18: price = 5 elif age < 65: price = 10 else: price = 5 print( "Your admission cost is " + str(price) + " dollars." )
当把列表名用作if语句的条件表达式时，Python将在列表至少包含一个元素时返回True，在列表为空时返回False。
requested_toppings = [] if requested_toppings: print( "not empty" ) else: print( "empty" )
‘‘‘列表为空，故打印empty‘‘‘
使用in表示包含于列表，not in表示不包含于列表。
available_toppings = [ ‘mushrooms‘, ‘olives‘, ‘green peppers‘, ‘pepperoni‘, ‘pineapple‘, ‘extra cheese‘ ] requested_toppings = [ ‘mushrooms‘, ‘french fries‘, ‘extra cheese‘ ] for requested_topping in requested_toppings: if requested_topping not in available_toppings: print( "Sorry, we don‘t have " + requested_topping + "." ) else: print( "Adding " + requested_topping + "." ) print( "\nFinished making your pizza!" )
输出为：
Adding mushrooms. Sorry, we don‘t have french fries. Adding extra cheese. Finished making your pizza!
参考书籍：《Python编程：从入门到实践》
2020-07-09
【Python基础知识】（四）比较运算符、逻辑运算符和if语句
原文：https://www.cnblogs.com/carl39/p/13275061.html