Python Lambda, map, filter

lambda arguments: expression

• This function can have any number of arguments but only one expression, which is evaluated and returned.
• One is free to use lambda functions wherever function objects are required.
• You need to keep in your knowledge that lambda functions are syntactically restricted to a single expression.
• It has various uses in particular fields of programming besides other types of expressions in functions.

# Example
def cube(y): 
    return y*y*y; 
  
g = lambda x: x*x*x 

print(g(7)) 
print(cube(5)) 

Using lambda with...

# filter() with lambda() 
li = [5, 7, 22, 97, 54, 62, 77, 23, 73, 61] 
final_list = list(filter(lambda x: (x%2 != 0) , li)) 
print(final_list) 

# map() with lambda()  
li = [5, 7, 22, 97, 54, 62, 77, 23, 73, 61] 
final_list = list(map(lambda x: x*2 , li)) 
print(final_list) 

# reduce() with lambda() 
from functools import reduce
li = [5, 8, 10, 20, 50, 100] 
sum = reduce((lambda x, y: x + y), li) 
print (sum) 

Map

map(fun, iter)

def addition(n): 
    return n + n 
  
# We double all numbers using map() 
numbers = (1, 2, 3, 4) 
result = map(addition, numbers) 
print(list(result)) 

# Double all numbers using map and lambda 
numbers = (1, 2, 3, 4) 
result = map(lambda x: x + x, numbers) 
print(list(result)) 

# Add two lists using map and lambda 
numbers1 = [1, 2, 3] 
numbers2 = [4, 5, 6] 
result = map(lambda x, y: x + y, numbers1, numbers2) 
print(list(result))  # [5, 7, 9]

# List of strings 
l = ['sat', 'bat', 'cat', 'mat'] 

# map() can listify the list of strings individually 
test = list(map(list, l)) 
print(test) 
# [['s', 'a', 't'], ['b', 'a', 't'], ['c', 'a', 't'], ['m', 'a', 't']]