How to loop and make array object in python? [duplicate]

collections.Counter is a handy builtin for this exact task:

from collections import Counter

lst = ['book1', 'book1', 'book1', 'book2', 'book2', 'book2', 'book2', 'book3', 'book3', 'book3', 'book3', 'book3']
print(dict(Counter(lst)))

Output:

{'book1': 3, 'book2': 4, 'book3': 5}

You could do something like this:

arr = ['book1', 'book1', 'book1', 'book2', 'book2', 'book2', 'book2', 'book3', 'book3', 'book3', 'book3', 'book3']

final = {}

# loop through each item in the array
# if it is NOT found in the dictionary, put it
# in the dictionary and give it a count of 1
# if it IS found in the dictionary, increment its value
for x in arr:
    if x in final:
        final[x] += 1
    else:
        final[x] = 1

print(final)

You can also use collections.Counter, which is made for exactly such thing.

from collections import Counter

li =['book1', 'book1', 'book1', 'book2', 'book2', 'book2', 'book2', 'book3', 'book3', 'book3', 'book3', 'book3']
print(dict(Counter(li)))
#{'book1': 3, 'book2': 4, 'book3': 5}