Python basic loop iteration

Question

Please explain to me how the variable, “count”, automatically associates itself with each index of the string, “Hello!”

greeting = 'Hello!'
count = 0

for letter in greeting:
    count += 1
    if count % 2 == 0:
        print(letter)
    print(letter)

print('done')

Basically, the following questions ask about the amount of times each letter of the string prints. After checking the discussion board, I found out that the logic is that the output is H = [1], e = [2], l = [3], l = [4], o = [5], ! = [6]. The thing is, I don’t understand why this happens.

Asked By: Sean D

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Source

Answer 1

Count does not associate with each index of the string.

'Hello' is a string that is composed of multiple characters at various indices:

`'Hello!'[0] = 'H'`
`'Hello!'[1] = 'e'`
`'Hello!'[2] = 'l'`
`'Hello!'[3] = 'l'`
`'Hello!'[4] = 'o'`
`'Hello!'[5] = '!'`

In the for loop, you are incrementing the variable count each time. Thus, in the first iteration, count=0. In the second iteration, count=1, and so on. Your loop is only checking to see if count is divisible by 2. If it is, then it prints out the letter corresponding to its value a second time. Thus, your code would print out

H
e
e
l
l
l
o
!
!
done

Answered By: victor

Answer 2

You asked:

Please explain to me how the variable, “count”, automatically associates itself with each index of the string, “Hello!”

But in your codes, there’s no need to use an if statement. And you should add the index or count to near of the item of the string.
Simply the codes should be something like:

greeting = 'Hello!'
count = 0
for item in greeting:
    print("item={}, index={}, count={:d}".format(item,greeting.index(item),count))
    count += 1

This will print out:

item=H, index=0, count=0
item=e, index=1, count=1
item=l, index=2, count=2
item=l, index=2, count=3
item=o, index=4, count=4
item=!, index=5, count=5

With the above codes you can see that the count is automatically associates with the each index of the string “Hello!”. However when you set the count value for example to 1, the 1’st index (Index0) string associates with when the count=1 then multiply it’s value until the end of the index with the for loop.

In “Hello!” string there is 6 items. The first item index always starts with 0. However in order to print a more beautiful display, like the ‘first item, second item, third item…’ you can add a count variable or you can use enumerate function like the below examples:

greeting = 'Hello!'
count = 1
for item in greeting:
    print("item={}, index={}, count={:d}".format(item,greeting.index(item),count))
    count += 1

greeting = 'Hello!'
for count,item in enumerate(greeting,1):
    print("item={}, index={}, count={:d}".format(item,greeting.index(item),count))

The last two codes will give you the same results which are:

item=H, index=0, count=1
item=e, index=1, count=2
item=l, index=2, count=3
item=l, index=2, count=4
item=o, index=4, count=5
item=!, index=5, count=6

Answered By: dildeolupbiten

Python basic loop iteration

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