What is the lambda function in Python?

Mehmet C. Aksoy

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Aug 5, 2024

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Hi, in this story I try to explain what is the lambda function(s) and how to use it.

The lambda keyword is used to create small, simple functions without giving them a name. These are called "lambda functions" or "anonymous functions."

Specifications

1. Anonymous: Lambda functions don’t have a name.
2. Single Expression: They can only contain one expression, not multiple statements.
3. Inline: They are often used in places where you need a small function for a short period of time.

lambda arguments: expression

Imagine you want a function that adds 10 to a number. Normally, you would write:

def square(x):
    return x**2

With a lambda function, you can write the same thing in one line:

square= lambda x: x**2

Lambda functions are often used when you need a small function for a short period, like in sorting or filtering lists.

numbers = [1, 2, 3, 4]
evens = filter(lambda x: x % 2 == 0, numbers)
print(list(evens))  # Output: [2, 4]