Transforming type Int64Index into an integer index in Python

Question

I'm quite new with python, however, I have to accomplish some assignment and I am struggling now on a problem. I try to get the index of the element in a table A when some other parameter from this table A corresponds to a value in a list B. The table A also already contains a column "index" where all elements are numerated from 0 till the end. Moreover, the values in tableA.parameter1 and listB can coincide only once, multiple matches are not possible. So to derive the necessary index I use a line

t=tableA.index[tableA.parameter1==listB[numberObservation]]

However, what I get as a result is something like:

t Int64Index([2], dtype='int64')

If I use the variable t in this format Int64Index, it doesn't suit for the further code I have to work with. Actually, I need only 2 as an integer number, without all this redundant rest.

Can somebody please help me to circumvent my problem? I am in total despair and would be grateful for any help.

Sandeep S · Accepted Answer · 2015-12-22 17:22:18Z

6

Try .tolist()

t=tableA.index[tableA.parameter1==listB[numberObservation]].tolist()

This should return

t = [2]

a list "without all the redundant rest" :)

answered Dec 22, 2015 at 17:22

Sandeep S

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2 Comments

QuackQuack Over a year ago

hi! I have tested your solution as well, thanks for your help. Especially it is useful if I have more than one match. Then t as a list should provide a good solution. However, I still have one problem. When I run your code, I get the error message 'Invalid frame count (= tableA.index[tableA.parameter1==listB])'. Moreover, when I debug the code and run only the command in IPython console without assigning the result to the variable - it works... Do you have any idea where the problem could be?

Sandeep S Over a year ago

I haven't faced the error 'Invalid frame count' with pandas. Is it possible for you to post a complete test program, with only the important details?

ShadowRanger · Accepted Answer · 2015-12-23 13:08:04Z

1

What package is giving you Int64Index? This looks vaguely numpy-ish, but numpy arrays define __index__ so a single element array of integer values will seamlessly operate as indices for sequence lookup.

Regardless, assuming t is supposed to be exactly one value, and it's a sequence type itself, you can just do:

t, = tableA.index[tableA.parameter1==listB[numberObservation]]

That trailing comma changes the line from straight assignment to iterable unpacking; it expects the right hand side to produce an iterable with exactly one value, and that one value is unpacked into t. If the iterable has 0 or 2+ values, you'll get a ValueError.

edited Dec 23, 2015 at 13:08

answered Dec 22, 2015 at 17:30

ShadowRanger

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