python search replace and join with delimiter

Question

I'm brand new and been going through some beginner code problems on checkIO. I finished this one today and am posting because I'm sure there is a much more elegant way to accomplish this, and I think this particular problem has a lot of useful applications. I would like to know what are the 'clean and efficient' ways to do it, or maybe what built-ins I haven't learned yet that I should explore. My version seems pretty ugly. Thanks!

Problem: take a tuple of phrases, anytime the word 'right' appears, replace it with 'left'. Create a new string combining all the phrases separated with a comma.

def left_join(phrases):
    """
        Join strings and replace "right" to "left"
    """
    phrases = list(phrases)
    newstr = ''
    for j, phrase in enumerate(phrases):
        if 'right' in phrase:
            mod = dict(enumerate(phrase))
            for key in mod:
                if mod[key] == 'r' and mod[key+4] == 't':
                    i = key
                    mod[i] = 'l'
                    mod[i+1] = 'e'
                    mod[i+2] = 'f'
                    mod[i+3] = 't'
                    mod[i+4] = ''
            switch = (list(mod.values()))
            phrase = ''.join(switch)
            if j == (len(phrases) - 1) or len(phrases) == 1:
                newstr += phrase
            else:
                newstr += phrase + ','
        else:
            if j == (len(phrases) - 1) or len(phrases) == 1:
                newstr += phrase
            else:
                newstr += phrase + ','
    return newstr

test1 = ("bright aright", "ok", "brightness wright",)
test2 = ("lorem","ipsum","dolor", "fright", "nec","pellentesque","eu",
         "pretium","quis","sem","nulla","consequat","massa","quis",)

Answer 1

Welcome to code review, good job using a docstring and trying to make your code readable.

• Space after a comma:

  test2 = ("lorem","ipsum","dolor", "fright", "nec","pellentesque","eu", "pretium","quis","sem","nulla","consequat","massa","quis",)

  According to PEP0008 which I recommend checking for being the official Python style guide: a space should be left after a comma for readability.

  Which should look like:

  test2 = ('lorem', 'ipsum', ...)

• Use descriptive names: names like left_join() newstr j are not describing the objects they represent ex: your function name can be def replace_word(words, word, new_word):

• Type hints: You may use type hints to indicate what are the inputs and outputs in the following way:

  def your_function_name(phrases: tuple) -> str:

• Docstrings: Good job using a docstring for your function, however the description is not very clear here's a better description and btw docstrings should indicate what the input and the output is (what the function parameters are and what it returns):

  def your_function_name(phrases: tuple, old_word: str, new_word: str) -> str:
      """
      Replace the old_word by the new_word if found in phrases.
      Args:
          phrases: Tuple of words.
          old_word: The word to replace.
          new_word: The replacement.
   Return:
       Joined string after replacements.
      """
  

• str.replace() and str.join() You can use the replace method to achieve the same results in a shorter code and since you're familiar with join():

  Instead of doing this for every letter in every word:

  else:
      newstr += phrase + ','
  

  You can do:

  ', '.join(words)
  

  Code might look like:

  And Note: You usually wouldn't be creating a function for such a simple task but use replace() and join() directly, I'm creating a function just for the sake of the example.

  def replace_word(phrases: tuple, old_word: str, new_word: str) -> str:
      """
      Replace the old_word by the new_word if found in phrases.
      Args:
          phrases: Tuple of words.
          old_word: The word to replace.
          new_word: The replacement.
   Return:
       Joined string after replacements.
      """
      return ', '.join(word.replace(old_word, new_word) for word in phrases)
  
  
  if __name__ == '__main__':           
      test1 = ("bright aright", "ok", "brightness wright",)
      test2 = ("lorem","ipsum","dolor", "fright", "nec","pellentesque","eu",
   "pretium","quis","sem","nulla","consequat","massa","quis",)
      print(replace_word(test1, 'right', 'left'))
      print(replace_word(test2, 'right', 'left'))
  

  Output:

  bleft aleft, ok, bleftness wleft

  lorem, ipsum, dolor, fleft, nec, pellentesque, eu, pretium, quis, sem, nulla, consequat, massa, quis

Answer 2

To replace the "right" instances from your phrases you could do it in a more elegant and quicker way using regular expressions.

#Import Regex Library
import re 
#Function to replace all "right" instances from your phrases
def replace_right(phrase): 
    phrase=list(phrase)
    for i in range(len(phrase)):
        #If the search of "right" is succesful
        if re.search(r"right",phrase[i]):
           #Substitutes "right" with "left"
           phrase[i]=re.sub(r"right","left",phrase[i])
    return phrase