Python中的‘lambda’关键字提供了一个便捷的途径去声明短小并匿名的函数。

# The lambda keyword in Python provides a
# shortcut for declaring small and 
# anonymous functions:

>>> add = lambda x, y: x + y
>>> add(5, 3)
8

# You could declare the same add() 
# function with the def keyword:

>>> def add(x, y):
...     return x + y
>>> add(5, 3)
8

# So what's the big fuss about?
# Lambdas are *function expressions*:
>>> (lambda x, y: x + y)(5, 3)
8

# • Lambda functions are single-expression 
# functions that are not necessarily bound
# to a name (they can be anonymous).

# • Lambda functions can't use regular 
# Python statements and always include an
# implicit `return` statement.

Lambda函数是单一表达式函数，即无需绑定名称。

Lambda函数不能使用常规的语句，通常包含一个隐式的返回语句。