Python: Map VS For Loop

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:

Python

# 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

1. 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:

   

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

   Example:
   

   Python

   # we use the keyword 'pass'
   # to simply get a for loop
   # with no content
   for i in range (10) :
       pass
3. 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 :
   

   Python

   # 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 !
   

4. for loop can exit before too. We can do that using break statement. Exiting before expected is not possible in map.
5. map generates a map object, for loop does not return anything.
6. syntax of map and for loop are completely different.
7. 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.

Let us see the differences in a tabular form -:

	Map()	forloop
1.	The map() function executes a specified function for each item in an iterable.	The for loop is used for iterating over a sequence.
2.	Its syntax is -: map(function, iterables)	It is used by using for keyword.
3.	In this, the item is sent to the function as a parameter.	It is used to execute a set of statements, once for each item in a list, tuple, set etc.
4.	It takes two parameters function and iterables.	Its syntax is -:  for var in iterable :               statements