python lambda

A lambda function is a small anonymous function.

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

Syntax

The expression is executed and the result is returned:

Example

Add 10 to argument a, and

return the result:



x = lambda a : a + 10print(x(5))

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Example

Add 10 to argument a, and

return the result:

Lambda functions can take any number of arguments:

Example

Multiply argument a with argument

b and return the

result:



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

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Example

Multiply argument a with argument

b and return the

result:

Example

Summarize argument a,

b, and c and

return the

result:



x = lambda a, b, c : a + b + cprint(x(5, 6,

2))

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Example

Summarize argument a,

b, and c and

return the

result:

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))



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Example

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))



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Example

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))



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Example

Use lambda functions when an anonymous function is required for a short period of time.

Test Yourself With Exercises

Exercise:

Create a lambda function that takes one parameter (a) and returns it.

Start the Exercise