Pandas data manipulation and counting on the same line

November 3, 2023

I am trying to count the number of books in a dataset whose publication year is equal to or greater than 2000.
Here is the format of the column:
publication_date = "dd/mm/yyyy"

Here is my code:

df[int(df["publication_date"][-4: 0]) >= 2000]["publication_date"].count()

I am receiving error like the one below:

TypeError                                 Traceback (most recent call last)
<ipython-input-31-ed1072acfb26> in <module>
----> 1 df[int(df["publication_date"][-4: 0]) >= 2000]["publication_date"].count()

/opt/conda/lib/python3.8/site-packages/pandas/core/series.py in wrapper(self)
    127         if len(self) == 1:
    128             return converter(self.iloc[0])
--> 129         raise TypeError(f"cannot convert the series to {converter}")
    130 
    131     wrapper.__name__ = f"__{converter.__name__}__"

TypeError: cannot convert the series to <class 'int'>

What should I do to fix it?

>Solution :

For speed up processing of datetime, you may have to convert it to datetime, then extract the year to make comparison.

import pandas as pd

data = {'publication_date': ['10/05/1999', '15/12/2005', '23/09/2002', '05/03/2000', '18/07/2008']}
df = pd.DataFrame(data)

df['publication_date'] = pd.to_datetime(df['publication_date'], format='%d/%m/%Y')
print(df[df['publication_date'].dt.year > 2000].count())