Use of Lambda function in python - filter()
Big Data Fundamentals with PySpark
Upendra Devisetty
Science Analyst, CyVerse
What are anonymous functions in Python?
Lambda functions are anonymous functions in Python
Very powerful and used in Python. Quite efficient with
map()andfilter()Lambda functions create functions to be called later similar to
defIt returns the functions without any name (i.e anonymous)
Inline a function definition or to defer execution of a code
Lambda function syntax
- The general form of lambda functions is
lambda arguments: expression
- Example of lambda function
double = lambda x: x * 2
print(double(3))
6
Difference between def vs lambda functions
- Python code to illustrate cube of a number
def cube(x):
return x ** 3
g = lambda x: x ** 3
print(g(10))
print(cube(10))
1000
1000
No return statement for lambda
Can put lambda function anywhere
Use of Lambda function in Python - map()
map() applies a function to all items in the input list
General syntax of map()
map(function, list)
- Example of map()
items = [1, 2, 3, 4]
list(map(lambda x: x + 2 , items))
[3, 4, 5, 6]
Use of Lambda function in python - filter()
filter() function takes a function and a list and returns a new list for which the function evaluates as true
General syntax of filter()
filter(function, list)
- Example of filter()
items = [1, 2, 3, 4]
list(filter(lambda x: (x%2 != 0), items))
[1, 3]
Let's practice
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