I want to get the elements in a list that match by substring while iterating over it. For instance, in following example list, i want to get "pass1", "pass2" matching elements and "pass3" as element that doesn't match. This is a simplified version of the list, as I need to iterate over the long list.
Please, let me know, what am I doing wrong in the following example.
keyList=["pass1_v1","pass1_v3","pass1_v5","pass2_v1","pass2_v3","pass3_v4"]
for x in keyList:
match=x.rsplit("_",1)[0] ## splitting the list elements seperated by "_"..eg:- pass1 to check how many elements match
if match in keyList:
print("matching are %s" %x) ## expecting to print eg:-pass1_v1 and pass1_v3
else :
print ("non matching are %s"%x) # expecting to print pass3_v4
You cannot use in membership testing with a substring; you'd have to loop over keyList again to test each substring.
It'd be far more efficient to grou all strings by prefix:
by_prefix = {}
for x in keyList:
by_prefix.setdefault(x.rsplit('_', 1)[0], []).append(x)
for prefix, matches in by_prefix.iteritems():
print 'Matches for {} are {}'.format(prefix, by_prefix[prefix])
This only prints the matching elements; all other keys are those that didn't match, but they'll be printed on their own:
>>> keyList = ["pass1_v1", "pass1_v3", "pass1_v5", "pass2_v1", "pass2_v3", "pass3_v4"]
>>> by_prefix = {}
>>> for x in keyList:
... by_prefix.setdefault(x.rsplit('_', 1)[0], []).append(x)
...
>>> for prefix, matches in by_prefix.iteritems():
... print 'Matches for {} are {}'.format(prefix, by_prefix[prefix])
...
Matches for pass2 are ['pass2_v1', 'pass2_v3']
Matches for pass1 are ['pass1_v1', 'pass1_v3', 'pass1_v5']
Matches for pass3 are ['pass3_v4']
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