Replace numeric values in a pandas dataframe

Question

Problem: Polluted Dataframe.
Details: Frame consists of NaNs string values which i know the meaning of and numeric values.
Task

Answer 1

You can do a round-conversion to str to replace the values and back.

df.astype('str').replace({'\d+': np.nan, 'nan': np.nan}, regex=True).astype('object')
#This makes sure already existing np.nan are not lost

Output

    0   1   2
0   abc cdf NaN
1   k   sum some
2   NaN NaN nothing