Python lambda function error when used with brackets

Question

I have a pandas data frame with 'Datetime' column containing timestamp information, I want to extract the hour information from the 'Datetime' column and add it to the hour column of the data frame.

I am confused since my code works if I write the lambda function without the braces

df['Datetime'].apply(lambda x: x.hour)

but, when I try this code instead

df['Datetime'].apply(lambda x: x.hour**()**)

I get the error "TypeError: 'int' object is not callable".

On the other hand when I use split function with lambda expression, it works completely fine with the braces -

df['Reasons'] = df['title'].apply(lambda x: x.split(':')[0])

You should use df['Datetime'].dt.hour. You don't need to do lambda x: for everything. It is often better to just used the pandas method without it. Same for the split. You should do: df['title'].str.split(':').str[0]) This is fundamental to writing good code with pandas, so it will greatly benefit you if you can keep these tips in mind. — David Erickson
– David Erickson, Commented Dec 12, 2020 at 0:35

Rajat Mishra · Accepted Answer · 2020-12-12 00:32:36Z

1

As mentioned by @Dani Mesejo, hour is an attribute of the datetime object. Hence it is working fine without brackets. Once you add brackets, it assumes the hour is a function and so you are getting that error.

You can read more about datetime object in its documentation

answered Dec 12, 2020 at 0:32

Rajat Mishra

3,7904 gold badges32 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python lambda function error when used with brackets

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related