CODEWITHSUNDEEP
python
drew moore
drew moore

Reputation: 32680

generating a string representation of a list of tuples

I have a list of tuples of form 

[("very", "ADJ"), ("slow", "ADJ"), ("programmer", "NOUN")]

My desired output is a single string of form: 

"very/ADJ slow/ADJ programmer/NOUN"

This being python, I know I can do this in a one-liner using the format() and join() methods, but I can't get the syntax quite right. My most recent attempt was: 

output_string = " ".join(["{0}/{1}".format(x) for x in list_of_tuples])

which threw an Index Error: tuple index out of range"

Upvotes: 1

Views: 42

Answers (3)

dawg
dawg

Reputation: 103844

You can use map too:

>>> ' '.join(map(lambda t: '{}/{}'.format(*t), li))
'very/ADJ slow/ADJ programmer/NOUN'

And, that same method without the lambda:

>>> ' '.join(map('/'.join, li))
'very/ADJ slow/ADJ programmer/NOUN'

Which works even if you have more than two elements in your tuples.

Upvotes: 0

Daniel Pryden
Daniel Pryden

Reputation: 60957

You want format(*x) so that the x tuple is expanded into arguments. Otherwise you are trying to call format with a single argument which is itself a tuple.

That said, if you know that these are all 2-tuples, I'd just go with the simpler:

output_string = " ".join(a + "/" + b for a, b in list_of_tuples)

Also note that there's no need to use a list comprehension to pass into join -- just use a generator comprehension instead.

Upvotes: 2

TigerhawkT3
TigerhawkT3

Reputation: 49318

words = [("very", "ADJ"), ("slow", "ADJ"), ("programmer", "NOUN")]
' '.join('/'.join((x,y)) for x,y in words)

Upvotes: 1

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