CODEWITHSUNDEEP
pythonif-statementfor-loop
JKnecht
JKnecht

Reputation: 241

Trying to learn basic for loop and/or if statement

I have just started to learn python and I wonder what is wrong with this for loop and/or if statement.

I am trying to loop through a list of words and if I find a word "right" I want to replace it with the word "left". 

def left_join(phrases):                
"""                 
    Join strings and replace "right" to "left"            
"""               

    mlist = list(phrases) 

    for word in mlist:

        if word == "right":
             word = "left"

    output = ','.join(mlist)
    return output    

phrases = ("left", "right", "left", "stop")
left_join(phrases)

I am supposed to get this

"left,left,left,stop"

but I get

"left,right,left,stop"

So "right" is not replaced with "left". Why?

Upvotes: 0

Views: 76

Answers (2)

Ren
Ren

Reputation: 2946

Try the following code:

def left_join(phrases):                
    """                 
         Join strings and replace "right" to "left"            
    """               

    mlist = list(phrases) 

    for i  in range(len(mlist)):

        if mlist[i] == "right":
            mlist[i] = "left"

    output = ','.join(mlist)
    return output    

phrases = ("left", "right", "left", "stop")
output = left_join(phrases)
print(output)

Upvotes: 1

zangw
zangw

Reputation: 48406

Quoting the official documentation on for loop,

An iterator is created for the result of the expression_list. The suite is then executed once for each item provided by the iterator, in the order of ascending indices.

So the mlist does not change, only word is changed here

Upvotes: 2

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