Python Lambda Function

 

Python Lambda

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A lambda function is a small anonymous function.

A lambda function can take any number of arguments, but can only have one expression.

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Syntax

lambda arguments : expression

The expression is executed and the result is returned:

Example

Add 10 to argument a, and return the result:

x = lambda a : a + 10
print(x(5))

Lambda functions can take any number of arguments:

Example

Multiply argument a with argument b and return the result:

x = lambda a, b : a * b
print(x(5, 6))

Example

Summarize argument a, b, and c and return the result:

x = lambda a, b, c : a + b + c
print(x(5, 6, 2))

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Why Use Lambda Functions?

The power of lambda is better shown when you use them as an anonymous function inside another function.

Say you have a function definition that takes one argument, and that argument will be multiplied with an unknown number:

def myfunc(n):
  return lambda a : a * n

Use that function definition to make a function that always doubles the number you send in:

Example

def myfunc(n):
  return lambda a : a * n

mydoubler = myfunc(2)

print(mydoubler(11))

Or, use the same function definition to make a function that always triples the number you send in:

Example

def myfunc(n):
  return lambda a : a * n

mytripler = myfunc(3)

print(mytripler(11))

Or, use the same function definition to make both functions, in the same program:

Example

def myfunc(n):
  return lambda a : a * n

mydoubler = myfunc(2)
mytripler = myfunc(3)

print(mydoubler(11))
print(mytripler(11))