Select columns in panda's dataframe that have an integer header

Question

I have a dataframe in pandas that looks like this:

   100  200  300  400
0    1    1    0    1
1    1    1    1    0

What I want to do is select specific columns from this data frame. But when I try the following code (the df_matrix being the dataframe displayed at the top) :

intermediary_df = df_matrix["100"]

It does not work and from what I can tell is because it is an integer. I tried to force it with str(100) but gave the same error as before:

File "pandas\_libs\hashtable_class_helper.pxi", line 958, in pandas._libs.hashtable.Int64HashTable.get_item
TypeError: an integer is required

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "A:\python project\venv\lib\site-packages\pandas\core\indexes\base.py", line 3078, in get_loc
    return self._engine.get_loc(key)
  File "pandas\_libs\index.pyx", line 140, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 164, in pandas._libs.index.IndexEngine.get_loc
KeyError: '100'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "pandas\_libs\index.pyx", line 162, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 958, in pandas._libs.hashtable.Int64HashTable.get_item
TypeError: an integer is required

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "A:/python project/testing/testing4.py", line 42, in <module>
    intermediary_df = df_matrix["100"]
  File "A:\python project\venv\lib\site-packages\pandas\core\frame.py", line 2688, in __getitem__
    return self._getitem_column(key)
  File "A:\python project\venv\lib\site-packages\pandas\core\frame.py", line 2695, in _getitem_column
    return self._get_item_cache(key)
  File "A:\python project\venv\lib\site-packages\pandas\core\generic.py", line 2489, in _get_item_cache
    values = self._data.get(item)
  File "A:\python project\venv\lib\site-packages\pandas\core\internals.py", line 4115, in get
    loc = self.items.get_loc(item)
  File "A:\python project\venv\lib\site-packages\pandas\core\indexes\base.py", line 3080, in get_loc
    return self._engine.get_loc(self._maybe_cast_indexer(key))
  File "pandas\_libs\index.pyx", line 140, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 164, in pandas._libs.index.IndexEngine.get_loc
KeyError: '100'

Does anyone know how to get around this? Thanks!

EDIT 1:

After trying to use intermediary_df = df_matrix[100] it worked as expecte. Btw, if someone else is facing this problem and wants to select multiple columns at the same time, you can use:

intermediary_df = df_matrix[[100, 300]]

and the output will be:

   100  300
0    1    0
1    1    1

Print your columns df_matrix.columns, check it is int or str — BENY
– BENY, Commented Jan 23, 2019 at 18:38
@W-B it seems to be integers. Output from console Int64Index([100, 200, 300, 400], dtype='int64') — Adrian
– Adrian, Commented Jan 23, 2019 at 18:39

harpan · Accepted Answer · 2019-01-23 18:46:23Z

1

Simply use below as in this case as your columns are int .

intermediary_df = df_matrix[100]`

If you want your columns to be accessed as str, Use:

df.columns = [str(x) for x in df.columns]

and then

df['100']

Output

0    1
1    1
Name: 100, dtype: int64

answered Jan 23, 2019 at 18:46

harpan

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3 Comments

Adrian Over a year ago

do you know how I can apply filters on columns with integer headers? I have tried df_matrix[df_matrix.100 == 1] , but that results into an error...

harpan Over a year ago

Just use df_matrix.loc[df_matrix[100] == 1]

harpan Over a year ago

No problem. @Adrian. Good luck!

Lucas Hort · Accepted Answer · 2019-01-23 18:58:12Z

1

I think your column type is an integer, but if it's not try this using DataFrame.loc

Example:

intermediary_df = df_matrix.loc[:,100]

or

intermediary_df = df_matrix.iloc[:,0]

edited Jan 23, 2019 at 18:58

answered Jan 23, 2019 at 18:41

Lucas Hort

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1 Comment

Adrian Over a year ago

The code did not work but using intermediary_df = df_matrix[100] makes it work

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