检查涉及Python中any（）函数的条件时键入Error

Question

First question on StackExchange... I've been learning Python to do some text analysis for a few months now, running Python 3.5 on a Mac, and I've got a problem with some code that looks like this:

from Levenshtein import distance
keywords = ['some', 'list']
line = 'some long string.'

for w in line.split():

    if condition_1 and not any(distance(w, k) < 2 for k in keywords):
        do_something

    elif condition_1 and any(distance(w, k) < 2 for k in keywords):
        do_something_else

    elif condition_2 and not any(distance(w, k) < 2 for k in keywords):
        do_a_third_thing

    else:
        do_somthing_completely_different

When the loop starts, condition_1 and condition_2 are False , so I would expect the first iteration of the loop to get to the fourth case and do that. But instead when it checks the third case it throws the following error message:

TypeError: distance expected two Strings or two Unicodes

If I go to that line in the debugger and check the type of w and the elements of the keywords list, they're all str . If I try just running the problematic command in the debugger, I get a NameError:

(Pdb) any(distance(w, k) < 2 for k in keywords)
*** NameError: name 'w' is not defined

If instead I put in the literal assigned to w everything is fine:

(Pdb) any(distance('some', k) < 2 for k in keywords)
True

Which makes me think it has something to do with how the generator function treats namespaces, but I'm not sure. I've tried substituting a builtin function for distance(w, k) , eg len(w + k) , just to check, and I get the same set of errors. I find the error particularly confusing as there appears to be no problem in checking the first two cases.

I could come up with a workaround, but I'd like to know what's actually going on here. Google and StackExchange have so far brought me no joy on this topic. Any thoughts or suggestions would be gratefully received.

Answer 1

you could make this a lot simpler by reformatting your if statements inside the loop and checking the type of W as follows:

print(" W contains '{}' and is a {} ".format(w, type(w)))
assert w,str

if condition_1:
    result = any(distance(w, k) < 2 for k in keywords):
    print(" Result contains '{}' and is a {} ".format(result,type(result)  

    if result:    
        do_something
    else:
        do_something_else

elif condition_2:
    if not any(distance(w,k) < 2 for k in keywords):
        do_a_third_thing

else:
     do_something_completely_different

I'm guessing your are getting these errors running with a different string than the example. Have you checked it actually has a value before you split it ?