Need Help Understanding For loops with Variables in Python

Question

I am going through the book Automate the Boring Stuff with Python, and need help understanding what's really happening with the code.

catNames = []

while True:
    print('Enter the name of cat ' + str(len(catNames) + 1) + ' (Or enter nothing to stop.):')
    name = input()
    if name == '':
        break
    catNames = catNames + [name]
print('The cat names are:')
for name in catNames:
    print('  ' + name)

now it makes sense until

for name in catNames:
        print('  ' + name)

I am only used to seeing for loops with range(), and this does not make sense to me. A detailed explanation would be highly appreciated thanks

Please consider accepting an answer; this tells others that the issue is resolved and helps people find the correct answer more easily. — M-Chen-3
– M-Chen-3, Commented Dec 21, 2020 at 18:39

FilipA · Accepted Answer · 2020-12-21 02:30:55Z

1

I will explain it to you on a simple example:

# You create some list of elements
list = [1, 2, 3, 9, 4]
  
# Using for loop you print out all the elements
for i in list:
    print(i)

It will print to the console:

And you can also do it by using range but you have to know the length of the array:

# You create some list of elements
list = [1, 2, 3, 9, 4]
  
# get the list length
length = len(list)
  
# Iterating the index
# same as 'for i in range(len(list))'
for i in range(length):
    print(list[i])

Console output will look the same as before

answered Dec 21, 2020 at 2:30

FilipA

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