Python Learning Notes (10) anonymous functions

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When we pass in a function, there are times when we don't need to explicitly define a function, and it's easier to pass in an anonymous function directly.

In Python, there is a limited amount of support for anonymous functions. As an example of a map() function, when calculating f (x) =x2, in addition to defining a f(x) function, you can also pass in an anonymous function directly:

>>> list (map (lambda x:x * x, [1, 2, 3, 4, 5, 6, 7, 8, 9])) [1, 4, 9, 16, 25, 36, 49, 64, 81]

By contrast, the anonymous function lambda x: x * x is actually:

def f (x):     return x * x

The keyword lambda represents an anonymous function, preceded by a colon, that x represents a function parameter.

The anonymous function has a restriction that there can be only one expression , without writing return , and the return value is the result of that expression .

There is a benefit to using anonymous functions because the function does not have a name and does not have to worry about function name collisions. In addition, the anonymous function is also a function object, you can assign the anonymous function to a variable, and then use the variable to invoke the function:

Lambda x:x * x>>> F<function <lambda> at 0x101c6ef28>> >> F (5)25

Python Learning Notes (10) anonymous functions