对于一个函数，只有一句话表示，那么就可以用lambda表达式表示，如：
def f(x): return x * x print(f(5))
out: 25
可以写为：
f = lambda x: x*x # 冒号左边为输入，右边是返回值，f是函数名 print(f(5))
out: 25
对于多个形式参数：
g = lambda x,y: x+y # 冒号左边为输入，右边是返回值，f是函数名 print(g(4,5))
out: 9
lambda用到比较多的地方是排序，如：
def get_four(my):
return my[2]
tuple_my = []
file = open("file.csv", "r")
for line in file:
Line = line.strip()
arr = line.split(",")
one = arr[1]
three = arr[3]
four = int(arr[4])
tuple_my.append( (one, three, four) )
tuple_my.sort(key=get_four)
for my in tuple_my:
print(my)可以写为：
get_four = lambda my: my[2]
tuple_my = []
file = open("file.csv", "r")
for line in file:
Line = line.strip()
arr = line.split(",")
one = arr[1]
three = arr[3]
four = int(arr[4])
tuple_my.append( (one, three, four) )
tuple_my.sort(key=get_four)
for my in tuple_my:
print(my)tuple_my = []
file = open("file.csv", "r")
for line in file:
Line = line.strip()
arr = line.split(",")
one = arr[1]
three = arr[3]
four = int(arr[4])
tuple_my.append( (one, three, four) )
tuple_my.sort(key=lambda my: my[2])
for my in tuple_my:
print(my)lambda也经常用在符合函数下，如：
def quadratic(a, b, c): return lambda x: a*x*x*x + b*x*x + c*x f = quadratic(3, -2, 4) print(f(5))
345
def quadratic(a, b, c): return lambda x: a*x*x*x + b*x*x + c*x print(quadratic(3, -2, 4)(5))
345