Question

In my code I have the following:

if all(requiredField in submittedFields for requiredField in requiredFields):
    # all required fields in submittedFields exist
else:
    # error handling

The goal is to check if a list of strings in requiredFields are all present in submittedFields

This works fine when requiredFields is a list of strings with length > 1. But, when you have something like

requiredFields = ('single element')

Then the for loop iterates over each character instead of the string itself.

So my question is, is there a more pythonic means of handling this other than

try: 
    requiredFields.sort()
    # requiredFields is a list of strings
except AttributeError:
    # requiredFields is a string list whose length == 1

Answer 1

Using python sets would be much more efficient:

submitted_fields = set(['length', 'width', 'color', 'single element'])
required_fields = set(['width', 'length'])
if submitted_fields >= required_fields:
    # all required fields in submittedFields exist
else:
    # error handling

Several optimizations make this fast:

• The hash table implementation of sets ensures a high likelihood of a match before doing a character by character equality test.
• If two strings are identical (the same object in memory), the identity check will bypass a character-by-character equality check.

Note. It looks like your original problem was with tuple notation. Steven Rumbalski addressed that very well. Of course, if you use sets, this becomes a non-issue.

Good luck with your field validation 🙂