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I would like to slice two columns in my data frame.

This is my code for doing this:

import pandas as pd df = pd.read_csv('source.txt',header=0) cidf = df.loc[:,['vocab','sumCI']]

This is a sample of data:

ID vocab sumCI sumnextCI new_diff 450 statu 3.0 0.0 3.0 391 provid 4.0 1.0 3.0 382 prescript 3.0 0.0 3.0 300 lymphoma 2.0 0.0 2.0 405 renew 2.0 0.0 2.0

Firstly I got this error:

KeyError: “None of [['', '']] are in the [columns]”'

What I have tried:

  • I tried putting a header with index 0 while reading the file,
  • I tried to rename columns with this code: 
    df.rename(columns=df.iloc[0], inplace=True)
  • I also tried this: 
    df.columns = df.iloc[1] df = df.reindex(df.index.drop(0))
  • Also tried comments in this link

None of the above resolved the issue.

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5 Answers 5

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11

By the print you posted, it seems like you have whitespaces as delimiters. pd.read_csv will read using , as default separator, so you have to explicitly state it:

pd.read_csv('source.txt',header=0, delim_whitespace=True)
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3

Maybe you have white spaces around your column names, double check your csv file

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This is also something to be aware of when using read_sql_query() : a column name in a table could have leading or trailing spaces. Ugh.
3

If you get this (or similar) error, check if your dataframe contains these columns. The following should be returning True in order for the indexing to work.

cols = ['vocab', 'sumCI'] set(df.columns).issuperset(cols)

If the above returns False, then you'll need to process the columns.

A common culprit is leading/trailing space, so try

df.columns = df.columns.str.strip()

Other common problems could be double underscore, double space or em dash (—) between words in legitimate column names. Then you may try regex to remove surplus space and underscores and replace em dash by en dash in column names, etc.

df.columns = df.columns.to_series().replace({r'\s+': ' ', r'_+': '_', r'—': '-'}, regex=True)
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2

simply write code to create a new CSV file and use a new file

 import numpy as np import pandas as pd import matplotlib.pyplot as plt pd.read_csv('source.txt',header=0, delim_whitespace=True) headers = ['ID','vocab','sumCI','sumnextCI','new_diff'] df.columns = headers df.to_csv('newsource.txt')
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2

You can try doing this:

pd.read_csv('source.txt',header=0, delim_whitespace=True)

If you have any white spaces in the data you're will get an error, so delim_whitespace is included to remove those in case they're in the data.

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