Python/Pandas, How to fill missing values of a column of duration times?

Question

My data (df) has a column "duration_time" with values in minutes and seconds like this:
10:43

These values range from 5 to 15 minutes.
The data type of this column is 'object'.
There is a couple of missing values in this column.

Is there a way to fill these missing values with the mean of this column?

I have tried different methods but no result.
df['duration_time'] = df['duration_time'].fillna(df['duration_time'].mean())
I got this message:
TypeError: can only concatenate str (not "int") to str

When I just try to calculate the mean of the column as this:
df['duration_time'].mean()
I get the following message:
TypeError: can only concatenate str (not "int") to str

Thank you in advance for your help!

Answer 1

I think your Series df['duration_time'] is not actually of datetime type. If I do:

df['duration_time']=pd.Series(['10:43',None,0])
df['duration_time'].fillna(df['duration_time'].mean())

Then I can reproduce your error. But if I wrap that series into a to_datetime(), then your code works:

df['duration_time']=pd.to_datetime(pd.Series(['10:43',None,0]))
df['duration_time'].fillna(df['duration_time'].mean())