Merging two DataFrames

The error message indicates that df2 is of type pd.Series. You need to convert df2 .to_frame() as .merge() needs a pd.DataFrame() input (see docs): while you probably also just could: Alternatively, you can use pd.DataFrame.join() which accepts a pd.Series.

Difference between data type ‘datetime64[ns]’ and ‘

datetime64[ns] is a general dtype, while <M8[ns] is a specific dtype. General dtypes map to specific dtypes, but may be different from one installation of NumPy to the next. On a machine whose byte order is little endian, there is no difference between np.dtype(‘datetime64[ns]’) and np.dtype(‘<M8[ns]’): However, on a big endian machine, np.dtype(‘datetime64[ns]’) would equal np.dtype(‘>M8[ns]’). So datetime64[ns] maps to either <M8[ns] or >M8[ns] depending on the endian-ness of the … Read more

Python: Convert timedelta to int in a dataframe

I would like to create a column in a pandas data frame that is an integer representation of the number of days in a timedelta column. Is it possible to use ‘datetime.days’ or do I need to do something more manual? timedelta column 7 days, 23:29:00 day integer column 7

Boolean Series key will be reindexed to match DataFrame index

Your approach will work despite the warning, but it’s best not to rely on implicit, unclear behavior. Solution 1, make the selection of indices in a_list a boolean mask: Solution 2, do it in two steps: Solution 3, if you want a one-liner, use a trick found here: The warning comes from the fact that the boolean vector df.a_col.isnull() is … Read more