CODEWITHSUNDEEP
pythonstringloopsfor-loop
Dan
Dan

Reputation: 8513

Adding a string in front of a string for each item in a list in python

I have a list of websites in a string and I was doing a for loop to add "http" in the front if the first index is not "h" but when I return it, the list did not change.

n is my list of websites h is "http"

for p in n:
    if p[0]!="h":
        p= h+ p
    else:
        continue
return n

when i return the list, it returns my original list and with no appending of the "http". Can somebody help me?

Upvotes: 8

Views: 15876

Answers (4)

YOU
YOU

Reputation: 123791

>>> n=["abcd","http","xyz"]

>>> n=[x[:1]=='h' and x or 'http'+x for x in n]

>>> n
['httpabcd', 'http', 'httpxyz']

Upvotes: 0

Ignacio Vazquez-Abrams
Ignacio Vazquez-Abrams

Reputation: 798536

n = [{True: '', False: 'http'}[p.startswith('h')] + p for p in n]

Don't really do this. Although it does work.

Upvotes: 0

Max Shawabkeh
Max Shawabkeh

Reputation: 38603

This could also be done using list comprehension:

n = [i if i.startswith('h') else 'http' + i for i in n]

Upvotes: 15

Alex Martelli
Alex Martelli

Reputation: 881567

You need to reassign the list item -- strings are immutable, so += is making a new string, not mutating the old one. I.e.:

for i, p in enumerate(n):
  if not p.startswith('h'):
    n[i] = 'http' + p

Upvotes: 3

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