How to change the same characters in a string to different values in python?

Question

I'm trying to implement a basic converting program, changing stars to either  or  depending on if they are the first or second of a pair, but regardless of what I do my program changes all the stars to  or .

line = "*ju*bil*ee*"
star_counter = 0
new_line = line
    for character in line:
         if character is "*":
            star_counter += 1
            if star_counter%2 == 0:
                new_line = line.replace(character, "</em>")
            else:
                new_line = line.replace(character, "<em>")

look up the definition of string.replace in python. problem solved: tutorialspoint.com/python/string_replace.htm. U need to limit the number of changes to 1 else ALL will be replaced. — Patrick Artner
– Patrick Artner, Commented Nov 13, 2017 at 21:00

zefixlluja · Accepted Answer · 2017-11-13 21:16:30Z

2

You're already looping over the input string character by character, so just append to the output (your toggling of opening/closing em tags is ok).

line = "*ju*bil*ee*"
expected = "<em>ju</em>bil<em>ee</em>"
star_counter = 0
new_line = ""
for character in line:
  if character is "*":
    star_counter += 1
    if star_counter%2 == 0:
      new_line += "</em>"
    else:
      new_line += "<em>"
  else:
    new_line += character

assert new_line == expected

edited Nov 13, 2017 at 21:16

answered Nov 13, 2017 at 21:07

zefixlluja

4785 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Joe Gagliardi Over a year ago

I'm not sure what the assert does, but the rest of the syntax works perfectly, thank you!

zefixlluja Over a year ago

assert ensures that an expression is true - otherwise it will throw an exception (makes it useful to "prove" in an easy way that a code snippet like above is correct)

Van Peer · Accepted Answer · 2017-11-13 21:10:41Z

0

new_line = "*ju*bil*ee*"
star_counter = 0
for character in new_line:
    if character is "*":
        if star_counter == 0:
            new_line = new_line.replace(character, "<em>", 1)
            star_counter=1
        else:
            new_line = new_line.replace(character, "</em>", 1)
            star_counter = 0
print(new_line)

Output

<em>ju</em>bil<em>ee</em>

answered Nov 13, 2017 at 21:10

Van Peer

2,1674 gold badges25 silver badges36 bronze badges

Comments

Barmar · Accepted Answer · 2017-11-13 21:11:30Z

0

You can do this with a regular expression substitution.

import re
new_line = re.sub(r'\*([^*]+)\*', r'<em>\1</em>', line)

The regular expression matches two * with some non-* characters between them, uses a capture group to capture the in-between text, and then substitutes that capture group between  and  in the result.

answered Nov 13, 2017 at 21:11

Barmar

789k57 gold badges555 silver badges669 bronze badges

Comments

Patrick Artner · Accepted Answer · 2017-11-13 21:57:37Z

0

Solution using cycle and imap from itertools:

from itertools import cycle, imap

em = iter(cycle(['<em>','</em>']))

def emEm(c):
    if c == '*':
        return em.next() 
    else:
       return c

line = imap(emEm,"*ju*bil*ee*") 
print(''.join(line))

cycle(['','']) lazyly repeats  and  as often as needed
emEm implements the decider logic for imap
imap executes the logic on each character of the string

Problem: with odd number of * you get a not well formed html - tag opens but does not close - but you could check that beforehand.

edited Nov 13, 2017 at 21:57

answered Nov 13, 2017 at 21:02

Patrick Artner

51.9k10 gold badges50 silver badges79 bronze badges

Collectives™ on Stack Overflow

How to change the same characters in a string to different values in python?

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related