Don't understand why one is working and not the other one-CodePudding

Can someone explain me why does the first function get trough and not the second one. I can't figure out why I cannot assign a new var to the parameter 'string_' I tried to search online but I can't find a name to that problem therefore I am running in circles.

First

def disemvowel(string_):
    for i in "aeiouAEIOU":
        string_ = string_.replace(i, "")
    return string_

Second

def disemvowel(string_):
    for i in "aeiouAEIOU":
        string = string_.replace(i, "")
    return string

CodePudding user response：

Sometimes a small print is better that an long explanation:

Option 1 (cumulative modifications):

def disemvowel(string_):
    for i in "aeiouAEIOU":
        string_ = string_.replace(i, "")
        print(i, string_)

disemvowel('aeizAEIZ')

a eizAEIZ
e izAEIZ
i zAEIZ
o zAEIZ
u zAEIZ
A zEIZ
E zIZ
I zZ
O zZ
U zZ

Option 2 (successive modifications):

def disemvowel(string_):
    for i in "aeiouAEIOU":
        string = string_.replace(i, "")
        print(i, string)

disemvowel('aeizAEIZ')

a eizAEIZ
e aizAEIZ
i aezAEIZ
o aeizAEIZ
u aeizAEIZ
A aeizEIZ
E aeizAIZ
I aeizAEZ
O aeizAEIZ
U aeizAEIZ

CodePudding user response：

The second function uses the unmodified caller argument for each replace, assigning to a different variable. As such, only the final replace (for 'U') has any effect. Reusing the argument (as you did in the first function) means you accumulate the changes rather than discarding each one in favor of the latest.

As a side-note, the work you're doing could be done in a single operation instead of requiring 10 separate replace calls:

# Done outside the function once so it can be reused without the expense of
# rebuilding it
# Creates a dict mapping all vowels to None, for use with str.translate,
# which interprets mapping to None as "delete this character"
_kill_vowels_table = str.maketrans('', '', 'aeiouAEIOU')
def disemvowel(string):
    return string.translate(_kill_vowels_table)

CodePudding user response：

It seems not working in the second code piece because you assigned the result of replace method to a different variable each time. If you type any input that finishes with U character you will see that it will be replaced with empty string.

def disemvowel(muz):
    for i in "aeiouAEIOU":
        elma = muz.replace(i, "")
    return elma
    
    
print (disemvowel('ovyeahbananaU'))

it returns ovyeahbanana

CodePudding user response：

In 2nd code. As string_ is unmodified on next for-loop run it won't remove the elements it removed before. So it will continue until last chr ("U" in your case). So it will only replace last chr with "".

def disemvowel_notworking(string_):
    for i in "aeiouAEIOU":
        string = string_.replace(i, "")
    return string

print(disemvowel_notworking("HELLO WORLD Ucheck"))

output

HELLO WORLD check