一个简单示例
cars = ['bmw', 'audi', 'toyota', 'subaru']
for car in cars:
if car == 'bmw':
print(car.upper())
else:
print(car.title())
BMW
Audi
Toyota
Subaru
条件测试
检查是否相等
# 检查是否相等 (区分大小写)
car = 'Audi'
print(car == 'audi')
# 不相等
print(car != 'audi')
False
True
比较数字
# 比较数字
age = 19
print(age == 19)
print(age != 19)
print(age < 21)
print(age <= 21)
print(age > 21)
print(age >= 21)
True
False
True
True
False
False
检查多个条件
# 检查多个条件
# and 同时成立; or 至少一个满足
age = 19
print(age > 10 and age < 19)
print(age > 10 or age < 19)
False
True
检查特定值是否包含在列表中
- in 包含
- not in 不包含
# 是否包含
# in 包含; not in 不包含
users = ['a001', 'a002', 'a003']
print('a003' in users)
print('a004' not in users)
True
True
布尔表达式
# 布尔表达式
status1 = True
status2 = False
确定列表不是空的
cars = []
if cars:
print("cars is not null")
else:
print("cars is null")
cars is null
列表是空, 做为条件是False
if 语句
简单 if 语句
if condition_1:
statement_block_1
if-else 语句
if condition_1:
statement_block_1
else:
statement_block_2
if-elif-else 结构
if condition_1:
statement_block_1
elif condition_2:
statement_block_2
else:
statement_block_3
多个elif 代码块
if condition_1:
statement_block_1
elif condition_2:
statement_block_2
elif condition_3:
statement_block_3
else:
statement_block_4
Python3 目录