python里的三元运算、for循环简写、匿名函数

1、三元运算

第一种

value = "变量1" if a>b else "变量2"

第二种

value = ("变量1","变量2")[a>b]

第三种

value = {"变量1","变量2"}[a>b]

传统写法

if a>b :
	value = "变量1"
else :
	value = "变量2"

2、for循环

单层for循环

# 传统写法
v = []
for r in [1,2,3]:
	v.apend(r+1)


# 简写
v = [r+1 for r in s]
# v 输出 [2, 3, 4]

双层for循环

rrr = [[1,2],[3,4]]


# 传统写法
v = []
for rr in rrr:
	for r in rr:
		v.apend(r+1)


# 简写
v = [r+1 for rr in rrr for r in rr]
# v 输出 [2, 3, 4, 5]

for循环+if

x = [1,2,3,4,5,6,7]

# 传统写法
for i in x：
	if i>3:
	 print(i)
		


# 简写
[print(i) for i in x if i>3 ]

3、匿名函数

例：

x = 3
v = (lambda k: k+3)(x)

# v 输出6

例：

v = list(map(lambda x: x * 2, [1, 2, 3, 4, 5]))

# v 输出： [2, 4, 6, 8, 10]