pandas.Dataframe.loc() and pandas.Dataframe.drop() not working-CodePudding

I am using pandas to create a ranklist. I created a csv file and used pandas to create a Dataframe. When I am slicing the dataframe using iloc method, its working fine, but its showing error with loc method. Similar error is also shown with drop method. When I am dropping the first column "Name", it works fine, but it again doesn't work with the remaining columns.

import pandas
#creating CRL
file1 = pandas.read_csv("csvfile_of_ranklist2.csv")
print(file1.index)
print(file1.columns)
file2 = file1.drop("Name",axis=1)
print(file1)
print(file2)

It gave the following output:

C:\Users\VIVEK PANDYA\Documents\Python programs>E:/python.exe "c:/Users/VIVEK PANDYA/Documents/Python programs/ranklist.py"
RangeIndex(start=0, stop=8, step=1)
Index(['Name', ' Category', ' Maths', ' Physics', ' Chemistry', 'Unnamed: 5'], dtype='object')
              Name  Category   Maths   Physics   Chemistry Unnamed: 5
0     Vivek Pandey        C1      89        78         100        NaN
1    Prateek Singh        C3     100        75          68
2     Yuvraj Singh        C3      88        92          36        NaN
3  Shaiqua Parveen        C2     100        52          32        NaN
4      Sana Afshan        C1      78        85          21        NaN
5    Shabber Islam        C2      89        23          56        NaN
6    Brahma Pandey        C4      78        54          62        NaN
7    Santosh Singh        C1      85        64          92        NaN
   Category   Maths   Physics   Chemistry Unnamed: 5
0        C1      89        78         100        NaN
1        C3     100        75          68
2        C3      88        92          36        NaN
3        C2     100        52          32        NaN
4        C1      78        85          21        NaN
5        C2      89        23          56        NaN
6        C4      78        54          62        NaN
7        C1      85        64          92        NaN

However if I try to drop "Category", it produces error:

import pandas
#creating CRL
file1 = pandas.read_csv("csvfile_of_ranklist2.csv")
print(file1.index)
print(file1.columns)
file2 = file1.drop("Category",axis=1)
print(file1)
print(file2)

C:\Users\VIVEK PANDYA\Documents\Python programs>E:/python.exe "c:/Users/VIVEK PANDYA/Documents/Python programs/ranklist.py"
RangeIndex(start=0, stop=8, step=1)
Index(['Name', ' Category', ' Maths', ' Physics', ' Chemistry', 'Unnamed: 5'], dtype='object')
Traceback (most recent call last):
  File "c:\Users\VIVEK PANDYA\Documents\Python programs\ranklist.py", line 8, in <module>
    file2 = file1.drop("Category",axis=1)
  File "E:\lib\site-packages\pandas\util\_decorators.py", line 311, in wrapper
    return func(*args, **kwargs)
  File "E:\lib\site-packages\pandas\core\frame.py", line 4906, in drop
    return super().drop(
  File "E:\lib\site-packages\pandas\core\generic.py", line 4150, in drop
    obj = obj._drop_axis(labels, axis, level=level, errors=errors)
  File "E:\lib\site-packages\pandas\core\generic.py", line 4185, in _drop_axis
    new_axis = axis.drop(labels, errors=errors)
  File "E:\lib\site-packages\pandas\core\indexes\base.py", line 6017, in drop
    raise KeyError(f"{labels[mask]} not found in axis")
KeyError: "['Category'] not found in axis"

Similarly, if i try to drop the indexes or slice indexes or columns using labels, it produces 'index not found in axis' or 'column not found in axis' error. I tried looking for any solution in pandas documentation, but I found no solution. How can this be solved?

CodePudding user response：

Get column names by file1.columns. Copy and use these column names. Your column names probably have whitespaces in the beginning or in the end.

CodePudding user response：

' Category' and most of the other column names have a leading whitespace. It says in the error KeyError: "['Category'] not found in axis", because 'Category' isn't a columnname.

A simple way to tidy up your column names is:

file.columns = [x.strip() for x in file.columns]

Now your Pandas Dataframe has columns without the leading whitespace and using 'Category' does work.