CODEWITHSUNDEEP
pythonstringloops
Dongsheng Xue
Dongsheng Xue

Reputation: 21

How can I compare two lists?

I'm asked to compare two different string and return the dis-matches. And if one string is longer than another, come out the extra characters. 

characters1=list(contents1)
characters2=list(contents2)
for (a,b) in zip(characters1, characters2):    
    if a != b:
        print('Mismatch at character', characters1.index(a), a, '!=', b)

Here is what I have done and I cannot figure out the extra part.

Upvotes: 1

Views: 91

Answers (5)

Vincent
Vincent

Reputation: 13415

>>> a = "xyz"
>>> b = "abcdef"
>>> a[len(b):] or b[len(a):]
'def'

Also, as @bereal pointed out, characters1.index(a) won't work as you expect. You could consider using enumerate:

for i, (a, b) in enumerate(zip(characters1, characters2)):    
    if a != b:
        print('Mismatch at character', i, ':', a, '!=', b)
print('Extra string:', characters1[i+1:] or characters2[i+1:])

Upvotes: 0

bereal
bereal

Reputation: 34272

I'd use itertools.izip_longest here, something like:

for idx, (a, b) in enumerate(izip_longest(s1, s2)):
    if a and b:
        if a != b:
            print 'Mismatch at {0}: {1} != {2}'.format(idx, a, b)
    else:
        suffix = (s1 if a else s2)[idx:]
        print 'Extra string: {0}'.format(suffix)
        break

Notice also that index() returns the first entrance of the item, so that might return a wrong result if the character repeats in the string. enumerate is the way to go. Converting strings to lists is also redundant, strings are already iterable.

Upvotes: 1

TigerhawkT3
TigerhawkT3

Reputation: 49320

This shows how to compare the two lists, and will properly compare two different strings of equal length:

a = ['abc', 'def', 'ghi']
b = ['abc', 'ddf', 'ghij']

for x,y in zip(a, b):
    if x!=y:
        print(x, y, x[len(y):] if len(x)>len(y) else y[len(x):])

Prints:

def ddf
ghi ghij j

Upvotes: 0

Eugene Soldatov
Eugene Soldatov

Reputation: 10135

Something like this:

if len(characters1) > len(characters2):
     print('Extra characters1: ', characters1[len(characters2):])
elif len(characters2) > len(characters1):
     print('Extra characters2: ', characters2[len(characters1):])

Upvotes: 0

konart
konart

Reputation: 1834

Compare their length:

if len(a)>len(b):
    print("a is longer than b by %s" % str(len(a)-len(b))) 
    print("Extra part is %s" % a[len(b):])
elif len(a)<len(b):
    print("a is shorter than b by %s" % str(len(b)-len(a)))
    print("Extra part is %s" % b[len(a):])

Upvotes: 0

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