the for loop is not iterating completely in python

Question

I want to traverse the for loop to find all the occurrences of "%" followed by an integer and replace them with another word.

 for x in format:
     if x is "%":
         finder = format.find("%")
         val = format[finder + 1]
         index = int(format[finder + 1])
         print("Index value is %d" % index)
         replace = args[index]
         print(replace)
         str = format.replace(val, replace)
 return str

If there is more than one "%" in format(i.e string) then only integer, is getting replaced.

Eg: format : "%1 greets %0" and args = "Bob", "Alex"

The output should be : "Alex greets Bob"

But what I'm getting is "Alex greets %0"

find() will only return the index of first occurance. Why dont you simply use a regex. m = re.search('%\d', format) — sjaymj62
– sjaymj62, Commented Jul 5, 2018 at 11:46

blue note · Accepted Answer · 2018-07-05 12:04:16Z

3

You need to write if x == "%", instead if x is "%". The is operator checks if they are actually the same object, not if they have the same content.

Another problem is the the .find('%') always returns the position of the first % in the string, regardless of where you are in you iteration. You could change your code to something like

for finder, x in enumerate(format):
     if x is "%":
         # you already know your position
         val = format[finder+1]
         ...

edited Jul 5, 2018 at 12:04

answered Jul 5, 2018 at 11:34

blue note

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1 Comment

Shsa Over a year ago

The problem is not solved yet. Eg: format = "Hello %0, %1" args = "Bob", "Alex" , it is still returning the same: "Hello Bob, 1".

Taohidul Islam · Accepted Answer · 2018-07-05 11:47:23Z

1

Your problem is in this line if x is "%":, is operator checks whether the both are same object. You need to use if x=='%' (== operator checks whether both are same value or not, it's not necessary to be both the same object to return True).

edited Jul 5, 2018 at 11:47

answered Jul 5, 2018 at 11:37

Taohidul Islam

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1 Comment

Shsa Over a year ago

The problem is not solved yet. Eg: format = "Hello %0, %1" args = "Bob", "Alex" , it is still returning the same: "Hello Bob, 1".

en_lorithai · Accepted Answer · 2018-07-05 11:58:06Z

0

There are definitely better ways of doing this, but if you want to do it with a loop then this will work.

item = '%1 greets %0'
args = ['bob','alex']
loc = 0
for x in item:  
    if x == "%":
        loc = item.find("%",loc)
        val ='%'+ item[loc +1]
        index = int(item[loc +1])
        replace = args[index]
        item = item.replace(val,replace)
        loc +=1

print(item)

Your solution doesn't work because you keep searching the same string (format) but saving the result in another string (str). The find method will therefore always find the first % in the format string.

One more comment i would like to add is to avoid naming your variables as python keywords like format and str.

answered Jul 5, 2018 at 11:58

en_lorithai

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