CODEWITHSUNDEEP
python
A. Vreeswijk
A. Vreeswijk

Reputation: 954

Python If statement doesn't return boolean but object

I have a problem. I have the following code:

strCommand = "There is a 20% chance that I fail the test"

# Splits command in words
words = nltk.word_tokenize(strCommand)
    
#Add tags to words
word_tags = nltk.pos_tag(words)

if (word for (word, pos) in word_tags if(pos[:2] == 'CD')):
    value = [word for (word, pos) in word_tags if(pos[:2] == 'CD')][0]
else:
    value = ""

This code splits the sentence into words and uses NLTK tagging, to know what type of word each word is. Then I want to ask if there is a word from the type CD (Cardinal Digit), if so... Then set the value to that word. Now when there is a number in my sentence, the code works, but when there isn't a number in it, it crashes because the array is empty where I set the value. I thought the code couldn't get there if it didn't found a number, but apparently the if statement doesn't return true or false.

How can I make it, that it does return true or false, so I won't enter the if?

Upvotes: 0

Views: 68

Answers (3)

Olvin Roght
Olvin Roght

Reputation: 7812

If you need just first entry, you can use next() with generator:

value = next((word for (word, pos) in word_tags if(pos[:2] == 'CD')), "")

It will return empty string if generator is empty. Also it's quite more effective, because you don't need to build whole list in memory twice, next() will stop iterating on first value returned. This means it stops when the first CD is found!

Upvotes: 1

khelwood
khelwood

Reputation: 59212

The expression in your if-statement is a generator expression. Generator expressions are truthy. If you want to check if a condition holds for any item in a sequence, use any(condition for element in sequence).

https://docs.python.org/3/library/functions.html#any

Upvotes: 1

rdas
rdas

Reputation: 21295

You should simplify your if-check. Right now, you're doing the the if-check on a generator expression:

(word for (word, pos) in word_tags if(pos[:2] == 'CD'))

Which is not what you want to do.

The simplest way to do what you want would be something like this:

reqd_words = [word for (word, pos) in word_tags if(pos[:2] == 'CD')]
if reqd_words:
    value = reqd_words[0]
else:
    value = ""

Upvotes: 1

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