Python: Map VS For Loop

Difficulty Level : Expert
Last Updated : 30 Jan, 2020

Map in Python :

Map is used to compute a function for different values ‘in a single line of code ‘ .
It takes two arguments, first is function name, that is defined already and the other is list, tuple or any other iterables .
It is a way of applying same function for multiple numbers .
It generates a map object at a particular location .
It works fast when we call an already defined function on the elements
```
 map(functionname, iterable)
```

Note: For more information refer to Python map() function.

for loop in Python :

We use for loop to repeat a block of code for fixed number of times .
Used when no results are required .
To perform sequential traversal .
Loop from 0 to n runs n+1 times .
```
 for var in iterable :
               statements 
```
Note: Here, var is the name given to iterating variable, iterable can be replaced by range() function and they can be of any data type . Statements are the step of actions to be performed .

Note: For more information, refer to Python For Loops.

Example:

# function to square a given number 
def squareNum (a) : 
    return a * a 
  
  
listt = [0, -1, 3, 4.5, 99, .08] 
  
# using 'map' to call the function 
# 'squareNum' for all the elements 
# of 'listt' 
x = map(squareNum, listt) 
  
# map function returns a map 
# object at this particular  
# location 
print(x)  
  
# convert map to list 
print(list(x))  
  
  
# alternate way to square all 
# elements of 'listt' using 
# 'for loop' 
  
for i in listt : 
    square = i * i 
    print(square) 

Output:

<map object at 0x7fe413cf9b00>
[0, 1, 9, 20.25, 9801, 0.0064]
0
1
9
20.25
9801
0.0064

Map vs for loop

Comparing performance , map() wins! map() works way faster than for loop. Considering the same code above when run in this ide.
Using map():

using for loop:
for loop can be with no content, no such concept exist in map() function.
Example:

# we use the keyword 'pass'

# to simply get a for loop

# with no content

for i in range (10) :

pass
There can be an else condition in for loop which only runs when no break statement is used. There is nothing like this in map.
Example :

# for loop with else condition



for i in range(10) :

    print(i)

else :

    print("Finished !")
Output :
```
0
1
2
3
4
5
6
7
8
9
Finished !
```
for loop can exit before too. We can do that using break statement. Exiting before expected is not possible in map.
map generates a map object, for loop does not return anything.
syntax of map and for loop are completely different.
for loop is for executing the same block of code for a fixed number of times, the map also does that but in a single line of code.

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