Pandas select only numeric or integer field from dataframe

Question

I have this Pandas dataframe (df):

     A    B
0    1    green
1    2    red
2    s    blue
3    3    yellow
4    b    black

A type is obje

Answer 1

Call apply on the dataframe (note the double square brackets df[['A']] rather than df['A']) and call the string method isdigit(), we then set param axis=1 to apply the lambda function row-wise. What happens here is that the index is used to create a boolean mask.

In [66]:
df[df[['A']].apply(lambda x: x[0].isdigit(), axis=1)]
Out[66]:
       A       B
Index           
0      1   green
1      2     red
3      3  yellow

Update

If you're using a version 0.16.0 or newer then the following will also work:

In [6]:
df[df['A'].astype(str).str.isdigit()]

Out[6]:
   A       B
0  1   green
1  2     red
3  3  yellow

Here we cast the Series to str using astype and then call the vectorised str.isdigit

Also note that convert_objects is deprecated and one should use to_numeric for the latest versions 0.17.0 or newer