For Loop And Zip In Python

I have a code that I am trying to understand and I need help. import numpy as np Class_numbers=np.array(['a','b','c']) students_per_class=np.array([10,20,30]) print('Students count

Solution 1:

zip allows you to iterate two lists at the same time, so, for example, the following code

letters = ['a', 'b', 'c']
numbers = [1, 2, 3]

for letter, number inzip(letters, numbers):
    print(f'{letter} -> {number}')

gives you as output

a ->1
b ->2
c ->3

when you iterate with zip, you generate two vars, corresponding to the current value of each loop.

Solution 2:

Q1: zip is used to merge 2 lists together. It returns the first element of each list, then 2nd element of each list, etc. This is a trick to consider the two lists as key and data to create a dictionary.

Q2: this is a dictionary (hash), using a method called "dict comprehension". It creates the dictionary shown as the output. If assigned to a variable d, d['a'] = 10, etc.

Solution 3:

just print the line you don't understand to make it clearer...

first we define 2 arrays

Class_numbers=np.array(['a','b','c'])
['a','b','c']students_per_class=np.array([10,20,30])
[10,20,30]

zip just add them together like

[('a', 10), ('b', 20), ('c', 30)]

now we iterate on each element with x and y and create a dict object (hash map) { key : value}

{'a': 10, 'c': 30, 'b': 20}

Solution 4:

zip is useful to enumerate the elements in the 2 different list and make a single list

example :

 x: y for x, y in zip(Class_numbers, students_per_class)

explanation:

• the element form Class_number is assigned to x which is a "Key" for the dictionary and the students_per_class is assigned to y which is a "value
• until the loop end it will iterate to dictionary.

Solution 5:

there is a trick in using zip:

letters = ('A', 'B', 'C')
numbers = ('1', '2', '3')
let_num = zip(letters, numbers)

use the list() function to display zip:

print(list(let_num))

above code will produce

[('A', '1'), ('B', '2'), ('C', '3')]

please note that, if you want to print again, this will not print anything since we already consumed the zip

print(list(let_num))