How to add columns to a new dataframe using a for loop?

Question

I want to create a new dataframe that will be exported to csv using selected columns from the existing dataframe.

I've tried using a for loop to add every column within range(14, var_x, 2). So all the even numbered columns after columns[14].

original code:

var_col_length=len(df.columns)

for x in range(14, var_col_length, 2):
    new_dataframe=df[df.columns[x]]

using append:

var_col_length=len(df.columns)

for x in range(14, var_col_length, 2):
    new_dataframe=new_dataframe.append(df[df.columns[x]])


TypeError: '<' not supported between instances of 'str' and 'int'

I either get only the last column, since as expected of the above code it keeps rewriting the dataframe "new_dataframe", when I tried using .append I get an error:

TypeError: '<' not supported between instances of 'str' and 'int'.

LayneSadler · Accepted Answer · 2019-08-22 19:19:45Z

1

Use .iloc

new_df = df.iloc[:, 14:var_col_length:2]

edited Aug 22, 2019 at 19:19

LayneSadler

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answered Aug 22, 2019 at 18:24

Nathan Furnal

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4 Comments

Mitch Over a year ago

How could I add an if or where statement to it?

Nathan Furnal Over a year ago

@Mitch The documentation on loc and iloc provides example to select rows and columns based on some conditions.

Mitch Over a year ago

Ya I can't find an example using endswith() and I'm getting an error when I try.

Nathan Furnal Over a year ago

@Mitch Scroll around for endswith and startswith on here, I'm sure you'll find something !

Ferran · Accepted Answer · 2019-08-22 18:26:48Z

0

import numpy as np
df[df.columns[np.arange(14,var_col_length,2)]]

answered Aug 22, 2019 at 18:26

Ferran

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2 Comments

Mitch Over a year ago

Thanks @Ferran how would you an "if" statement to that?

Ferran Over a year ago

df.columns.isin() for filtering columns with conditions

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