how to put a condition in a loop that checks all cells one by one?-CodePudding

I have a list of columns of my dataframe named "column". I want to calculate the difference between these columns and df['DOB'] I mean if it contins 0 I want to return 0 and if it is not 0 then calculate the difference.this is the loop for that:

    if df[df[col]>0]:
        df['diff_age' col]=df[col]-df['DOB']
    else:
         df['diff_age' col]=0

but I got this error: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

CodePudding user response：

dataset view needed for condition. can you just share!

CodePudding user response：

IIUC, you can vectorize your operation:

column = ['col1', 'col2', 'col3']
df[column] = df[column].where(df[column] > 0).add(df['DOB'], axis=0).fillna(0, downcast='int')
print(df)

# Output
   col1  col2  col3  DOB
0     0     4     4    3
1     0     5     6    3
2     0     0     7    3
3     0     0     0    0
4     5     5     0    3
5     0     8     0    4
6     2     2     0    0
7     0     3     4    1
8     0     0     0    3
9     4     0     0    3

Minimal Reproducible Example:

>>> df
   col1  col2  col3  DOB
0    -2     1     1    3
1    -4     2     3    3
2    -1    -3     4    3
3    -5    -2    -5    0
4     2     2    -1    3
5    -3     4     0    4
6     2     2    -4    0
7    -5     2     3    1
8     0    -3    -5    3
9     1     0    -2    3