Zip, Enumerate

Mutable and Immutable Objects

Zip

The zip() function take iterables (can be zero or more), makes iterator that aggregates elements based on the iterables passed, and returns an iterator of tuples.

# Example 1
# initializing lists
name = [ "Manjeet", "Nikhil", "Shambhavi", "Astha" ]
roll_no = [ 4, 1, 3, 2 ]
marks = [ 40, 50, 60, 70 ]

# using zip() to map values, converting map value to print as set
mapped = set(zip(name, roll_no, marks))
print(mapped)
print(list(zip(*mapped)))
print("-"*50)

namz, rollz, markz = list(zip(*mapped))
print(namz)
print(rollz)
print(markz)

>>
{('Nikhil', 1, 50), ('Shambhavi', 3, 60), ('Astha', 2, 70), ('Manjeet', 4, 40)}
[('Nikhil', 'Shambhavi', 'Astha', 'Manjeet'), (1, 3, 2, 4), (50, 60, 70, 40)]
--------------------------------------------------
('Nikhil', 'Shambhavi', 'Astha', 'Manjeet')
(1, 3, 2, 4)
(50, 60, 70, 40)

# Example 2
players = [ "Sachin", "Sehwag", "Gambhir", "Dravid", "Raina" ]
scores = [100, 15, 17, 28, 43 ]

for pl, sc in zip(players, scores):
    print ("Player :  %s     Score : %d" %(pl, sc))

# Example 3 - unzipping values
# Unzipping means converting the zipped values back to the individual self as they were.
# This is done with the help of “*” operator.

# initializing list of tuples
test_list = [('Akshat', 1), ('Bro', 2), ('is', 3), ('Placed', 4)]
print ("Original list is : " + str(test_list))

# using zip() and * operator to
# perform Unzipping
res = list(zip(*test_list))
print ("Modified list is : " + str(res))

>>
Original list is : [('Akshat', 1), ('Bro', 2), ('is', 3), ('Placed', 4)]
Modified list is : [('Akshat', 'Bro', 'is', 'Placed'), (1, 2, 3, 4)]

Enumerate

Enumerate is a built-in function of Python.

• It adds a counter to an iterable and returns it in a form of enumerate object
• enumerate also accept an optional argument. The optional argument allows us to tell enumerate from where to start the index.

my_list = ['apple', 'banana', 'grapes', 'pear']

for counter, value in enumerate(my_list):
    print(counter, value)

print("-"*50)
for c, value in enumerate(my_list, 100):
    print(c, value)

print("-"*50)
print(list(enumerate(my_list)))

>>
0 apple
1 banana
2 grapes
3 pear
--------------------------------------------------
100 apple
101 banana
102 grapes
103 pear
--------------------------------------------------
[(0, 'apple'), (1, 'banana'), (2, 'grapes'), (3, 'pear')]
<enumerate object at 0x7f1ae0392dc8>