Lambda functions
Intermediate Python for Developers
Jasmin Ludolf
Senior Data Science Content Developer
Simple functions
def average(values):
average_value = sum(values) / len(values)
return average_value
Lambda functions
lambdakeyword- Represents an anonymous function
lambda
Lambda functions
lambdakeyword- Represents an anonymous function
lambda arguments
Lambda functions
lambdakeyword- Represents an anonymous function
lambda arguments:
Lambda functions
lambdakeyword- Represents an anonymous function
$$
lambda arguments: expression
- Convention is to use
xfor a single argument - The
expressionis the equivalent of the function body - No
returnstatement is required
$$
- Can be stored as a variable
Creating a lambda function
# Lambda average function
print(lambda x: sum(x) / len(x))
<function <lambda> at 0x7f11ab813d80>
# Custom average function
def average(x):
return sum(x) / len(x)
print(average)
<function average at 0x7f11ab813ec0>
Using lambda functions
# Get the average
(lambda x: sum(x) / len(x))
Using lambda functions
# Get the average
(lambda x: sum(x) / len(x))([3, 6, 9])
$$
$$
# Print the average
print((lambda x: sum(x) / len(x))([3, 6, 9]))
6.0
Storing and calling a lambda function
# Store lambda function as a variable average = lambda x: sum(x) / len(x)# Call the average function print(average([3, 6, 9]))
6.0
Multiple parameters
# Lambda function with two arguments power = lambda x, y: x**y# Raise 2 to the power of 3 print(power(2, 3))
8
Lambda functions with iterables
map()applies a function to all elements in an iterable
names = ["john", "sally", "leah"]# Apply a lambda function inside map() capitalize = map(lambda x: x.capitalize(), names)print(capitalize)
<map object at 0x7fb200529c10>
# Convert to a list
print(list(capitalize))
['John', 'Sally', 'Leah']
Custom vs. lambda functions
| Scenario | Function Type |
|---|---|
| Complex task | Custom |
| Same task several times | Custom |
| Performed once | Lambda |
| Simple task | Lambda |
Let's practice!
Intermediate Python for Developers
