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Python Python Collections (Retired) Lists Redux Manipulating Lists

Posted by jabbar mehdipour
jabbar mehdipour
Courses Plus Student 604 Points

what's the problem with this code ? Should in the_list all non-integer values to be removed.

lists.py 
the_list = ["a", 2, 3, 1, False, [1, 2, 3]]

index = 0

while True:
  if type(the_list[index]) != int:
    del the_list[index]
  index = index + 1
  if index >= len(the_list):
    break

2 Answers

nightingale
nightingale
2,056 Points

Remember when you delete and index it shift everything over so what you should try is:

if type(the_list[index]) != int: del the_list[index] else: index = index + 1

So it only increment when an int is found. For example slot 0 will get deleted and when you do that slot 1 will become 0 and so forth. So when it delete False the list then moves to the False position and since you have it to increment the list gets skipped.

jabbar mehdipour
jabbar mehdipour
Courses Plus Student 604 Points

Right. Thank you so much for your response.

Unsubscribed User
Unsubscribed User
3,273 Points
Unsubscribed User
Unsubscribed User
3,273 Points

While your method will work with the afore mentioned tweaks I think you would be better served by a for loop here since it would eliminate the need for your index = index + 1.

the_list = ["a", 2, 3, 1, False, [1, 2, 3]] output_list = []

for value in the_list: if type(value) != int: output_list.append(value)

This will be a bit faster for a short list like this and will make your code a bit nicer to look at.

If you really want to keep your code style then one more simple change to make (in addition to what nighingale already told you) would be to replace index = index + 1 with index += 1. It does exactly the same thing but is a bit shorter, easier to look at, and quicker to type.

jabbar mehdipour
jabbar mehdipour
Courses Plus Student 604 Points

aha , tanx . Finally, I wrote this code:

lists.py 
the_list = ["a", 2, 3, 1, False, [1, 2, 3]]

index = 0
while index < len(the_list):
  if type(the_list[index]) != int:
    del the_list[index]
    index -=1
  index += 1

print(the_list)

And another question: Is there a for loop like C++ language in Python? like this :

forLoop.cpp 
for(int counter = 0 ; counter < sampleValue ; counter++){
     //code...
}
Unsubscribed User
Unsubscribed User
3,273 Points

That looks kind of like a list comprehension...

I will admit I haven't done any work with C++ since I was in highschool (many many many years ago) and I didn't really get programming at all then so I can't really say that this is what you are asking for.

If I was you I'd look up some tutorials on list comprehension as I think that is what you are looking for.

Actually I'm surprised that the treehouse python track doesn't include a section on list comprehensions. What's up with that Mr. Love?

Meme about list comprehension