Why is the second ' for loop' not the changing the items of the list to 'hello' whereas the first one changes as intended?

Question

nums = [1, 2, 3]
for i in range (len(nums)):
nums[i]='hi'
print(nums)
for i in nums:
i='hello'
print(nums)

Output:
['hi', 'hi', 'hi']
['hi', 'hi', 'hi']

Answer 1

Because in the first loop, you are using the index to directly change the array. In the second loop, a local variable i is created and you are changing that local variable.

Answer 2

In the second loop you are making i be 'hello' for each iteration but you are not putting it back into the list. To see what's going on, insert print() functions into the loop, e.g.

nums = [1, 2, 3]
for i in nums:
print(i)
i='hello'
print(i)
print(nums)

Answer 3

for i in nums:
suggest me a list comprehension...

print(['hello' for i in nums])

but in this way a parallel list is generated, the original one is untouched

Answer 4

David Ashton Bilbo Baggins XXX Thank you. But how do I put 'hello' in the list in place of the already existing items instead of just creating a copy or temporary list.

Answer 5

just reassign the temporary list ;)

nums = ['hello' for i in nums]
print(nums)