CODEWITHSUNDEEP
python
pocketfullofcheese
pocketfullofcheese

Reputation: 8847

Why am I getting a "type 'bool' is not iterable" if I am not trying to iterate?

Could someone with superior python skills please explain why am I getting a "bool is not iterable" error, when I am only doing some dict lookups and comparisons?

This is the last line of the stack trace:

---> 54     if 'identifiers' in document and 'doi' in document['identifiers'] and document['identifiers']['doi'] == row['doi']:
     55         print 'Found DOI'
     56         return True

TypeError: ("argument of type 'bool' is not iterable", u'occurred at index 2914')

Is best practice to use a try/except to attempt to read my dict and catch if the key does not exist?

Upvotes: 2

Views: 8436

Answers (3)

gog
gog

Reputation: 11347

When an object doesn't provide contains(), in attempts to iterate it (https://docs.python.org/2/reference/expressions.html#membership-test-details)

>>> print 1 in True
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: argument of type 'bool' is not iterable
>>>

The problem seems to be that the key does exist, but has the wrong type, so the in check isn't helpful here. Generally, in python it's better to follow EAFP and handle an exception instead of trying to pre-check everything.

Upvotes: 9

Pranav Raj
Pranav Raj

Reputation: 873

document['identifiers'] is a bool type, and the 'in' is trying to iterate over a bool variable which is giving you this error.

Upvotes: 1

thumbtackthief
thumbtackthief

Reputation: 6221

I don't think this is the cause of your error, but you can use the get method:

dict.get(key, default=None)

You can define an optional default value to return if the key is not present, and it won't trip an error.

Upvotes: -1

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