How to pass index to function Python Pandas

Question

I am trying to pass an index from a df into my function so that my function can run through all of the rows of the df and provide the output which is a int in a new column called "TDNumber'.

Here is the code

 def createTdnumber(onedfindex):
    header.index    
    maski = header.index < onedfindex 
    finder = header[maski]
    tdnumber = max(finder.index)
    return tdnumber

df['TDNumber'] = df.index.apply(createTdnumber())

as indicated below The mask should receive a number such as 227 That 227 would be one of the numbers provided by df.index.apply to the function

 def createTdnumber(onedfindex):
    header.index    
    maski = header.index < 227 
    finder = header[maski]
    tdnumber = max(finder.index)
    return tdnumber

df['TDNumber'] = df.index.apply(createTdnumber())

This code generates the error 'Int64Index' object has no attribute 'apply'

For the 'Int64Index' how do I pass those numbers one at a time to my function?

header.index

my output is

 Int64Index([0, 226, 470, 659, 863, 1108], dtype='int64')

from shx2 solution when I run

df.index.to_series()

The output is:

1          1
2          2
3          3
4          4
5          5
6          6
7          7
8          8
9          9
227      227
228      228
229      229
230      230
471      471
472      472
473      473
474      474
475      475
476      476

acushner · Accepted Answer · 2014-11-17 18:59:25Z

1

Index types don't have an apply method, but Series does.

To apply a function to your index, you can convert it to a series first, using its to_series method:

df['TDNumber'] = df.index.to_series().apply(createTdnumber)

edited Nov 17, 2014 at 18:59

acushner

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answered Nov 17, 2014 at 16:51

shx2

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4 Comments

Erich Over a year ago

When I run the solution I get the error. "createTdnumber() takes exactly 1 argument (0 given) " I thought that with .apply I didn't need to put anything in the function parenthesis? Is there some other transformation that needs to occur? I posted some additional information in the question

Paul H Over a year ago

maybe try: df['TDNumber'] = df.index.to_series().apply(lambda r: createTdnumber(r)) (@Erich)

Paul H Over a year ago

or maybe just df['TDNumber'] = df.index.to_series().apply(createTdnumber) (@Erich)

Erich Over a year ago

race['Tdnumber'] = race.index.to_series().apply(lambda r: createTdnumber(r)) This worked @Paul H

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