我的代码没有显示“找不到匹配项”，为什么？

Question

This is my code. It doesn't print ''No matches found'' I think that it has to do with the section start program

scores_and_similarities = "somestring"  # value can be empty
similarities = scores_and_similarities.split(',')
if similarities == '':
    print('\tNo matches found')
for similarity in similarities:
    print('\t%s' % similarity)

Answer 1

str.split returns a list not a string . Test your value using truthiness instead:

similarities = scores_and_similarities.split(',')
if not similarities  # better than if similarities == []
    print('\tNo matches found')

note that str.split returns an empty list just when the input string is empty. So you could test

if not scores_and_similarities:
   print('\tNo matches found')
else:
   # split and process

although I suspect that you're expecting str.split to return empty list if string doesn't contain a comma but it's not:

>>> ''.split(",")
>>> []
>>> 'iii'.split(",")
['iii']

so maybe you want to test if , is in the string (note: testing if splitted string has 1-length does the same:

if ',' not in scores_and_similarities:
   print('\tNo matches found')

Answer 2

This is because after the split it returns empty list [] not an empty string '' .

scores_and_similarities = "somestring"  # value can be empty
similarities = scores_and_similarities.split(',') # empty list is returned
if similarities == '': # [] is not equal to ''
    print('\tNo matches found')
for similarity in similarities:
    print('\t%s' % similarity) # so answer is this