Python : Exiting for loop?

Question

I did some research on SO and am aware that many similar questions have been asked but I couldn't quite get my answer. Anyway, I'm trying to build a library to "encrypt" a string with "Cesar's number" technique which means I have to take the string and replace each letters with another letter X positions away in the alphabet (I hope that makes sense). Here's my code:

from string import ascii_lowercase, ascii_uppercase

def creer_encodeur_cesar(distance):
    
    retour = lambda x: encodeur_cesar(x, distance)
    return retour

def encodeur_cesar(string, distance):
    tabLowerCase = list(ascii_lowercase)
    tabUpperCase = list(ascii_uppercase)
    tabString = list(string)
    
    l_encodedStr = []
    
    for char in tabString:
        position = 0
        if char == " ":
            pass
        elif char.isupper():
            #do something
               
        elif char.islower():
            for ctl in range(0, len(tabLowerCase)):
                position = ctl
                if char == tabLowerCase[ctl]:
                    if (ctl + distance) > 26:
                        position = ctl + distance - 25
                    char = tabLowerCase[position + distance]
                    l_encodedStr.append(char)
                    #How to break out of here??
                    
        
        encodedStr = str(l_encodedStr)

        return encodedStr

encodeur5 = creer_encodeur_cesar(5)
print(encodeur5("lionel"))

So, in my second elif statement, I want to break once I have successfully found and encrypted a character instead of looping through the whole alphabet. I have tried to use break but it broke out of the main for loop. Not what I want. I saw that I could use try except and raise but I don't quite know how I could do that and is it a good idea?

What's the best way to do this? What are the good practices in this case?

Any help would be appreciated and thanks in advance!

from which loop do you want to break out of? This one: for char in tabString: or this one: for ctl in range(0, len(tabLowerCase)):? — Dominik Schmidt
– Dominik Schmidt, Commented Feb 21, 2016 at 18:26
the for ctl in range(0, len(tabLowerCase)): one. Sorry I wasn't more clear — Gaboik
– Gaboik, Commented Feb 21, 2016 at 18:33
just using break should be enough. break always exits out of the deepest (nested) loop. — Dominik Schmidt
– Dominik Schmidt, Commented Feb 21, 2016 at 18:44
You can iterate directly over strings. for char in string, and for ctl, char in enumerate(ascii_lowercase). — chepner
– chepner, Commented Feb 21, 2016 at 19:10

wpercy · Accepted Answer · 2016-02-21 18:39:53Z

5

You can use the continue keyword.

From the docs:

>>> for num in range(2, 10):
...     if num % 2 == 0:
...         print "Found an even number", num
...         continue
...     print "Found a number", num
Found an even number 2
Found a number 3
Found an even number 4
Found a number 5
Found an even number 6
Found a number 7
Found an even number 8
Found a number 9

edited Feb 21, 2016 at 18:39

answered Feb 21, 2016 at 18:14

wpercy

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3 Comments

Gaboik Over a year ago

But under what condition would my program enter the else statement? When it reaches the break?

wpercy Over a year ago

@Gaboik I'm so sorry, I pasted the wrong snippet when I added the output. Basically, you can put code after the continue that you only want executed if the continue doesn't get executed.

Gaboik Over a year ago

Okay that makes more sense :) Thanks!

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