def name (parameter 1, parameter 2, parameter 3, ...)
You can customize some of the functions they need to simplify their work.
Such as: a calculation function Custom
def mycount(a,b,c):
y=a+b-c
return y
Call: mycount (5,3,1) is output: 5 + 3-1 = 7
lambda: anonymous functions for simple function definition
Usage: lambda x: x + x colon: result is returned back to the operation of the object x
Lambda anonymous functions often apply () appear together, to achieve vertical or horizontal rows of operations
apply (lambda x: x + 1, axis = 0 or axis = 1) axis = 0 is the default application function a longitudinal, axis = 1 represents the lateral application function