python学习之路四--if语句

python if语句

1.简单的使用if语句

li = ["a","b","c","d"]
for l in li :
if l == "a":
print(l.upper())
elif l == "b":
print(l.title)
else l == "c":
print(l)

2.检查是否相等时不考虑大小写

在python中两个大小写不同的值会被视为不相等

如果大小写无关重要，则将他们都变成小写来比较

a = "Alpha"
b = "alpha"

a.lower() == b

3.检查多个条件

使用and 检查几个条件是否同时满足条件

使用or 检查多个条件是否有一个满足条件

4.检查特定值是否在列表中

a = ["a","b","c"]
"a" in  a
True
"d" in a
False

5.检查特定值不在列表中

a = ["a","b","c"]
"a" not in  a
False
"d" not in a
True

6.使用多个elif代码块

age = 13
if age < 4:
prince = 0
elif age <18:
prince = 5
elif age <65:
prince = 10
else:
prince = 5
print("Your admission cost $"+str(prince)+".")

7.当列表为空时   表示False