Creation of a time-only frequency in Python

Question

I'm trying to generate a frequency DataFrame in Jupyter/Python of HH:MM:SS elements of a datetime column.

Aside from iterating over all HH:MM:SS combinations and counting them (I need to include 0 values), is there a function in Python that can do it for me?

.value_counts() creates what I need, however, 0 values are not included.

Many thanks, in advance, for your assistance :)

EDIT: sample data:

TransactionID	DateTime	Date	Time
012sad9j20j	01/01/22 04:23:32	01/01/22	04:23:32
938hfd82dj2	07/04/22 23:12:59	07/04/22	23:12:59
s9j20jd902j	18/05/22 13:44:19	18/05/22	13:44:19

Expected to generate a dataframe containing:

Time	Count
04:23:31	0
04:23:32	1
04:23:33	0

Answer 1

Here's a solution:

from pandas import DataFrame
from datetime import datetime, time

df = DataFrame([
    {'TransactionID': 'xyz1', 'DateTime': datetime(year=2022, month=6, day=16, hour=13, minute=1, second=2)},
    {'TransactionID': 'xyz1', 'DateTime': datetime(year=2022, month=6, day=16, hour=13, minute=3, second=4)},
    {'TransactionID': 'xyz1', 'DateTime': datetime(year=2022, month=6, day=17, hour=13, minute=5, second=6)},
    {'TransactionID': 'xyz1', 'DateTime': datetime(year=2022, month=6, day=18, hour=13, minute=1, second=2)},
    {'TransactionID': 'xyz1', 'DateTime': datetime(year=2022, month=6, day=19, hour=13, minute=3, second=4)}
])

times = DataFrame(df['DateTime'].dt.time).groupby(['DateTime'])['DateTime'].count()

time_counts = DataFrame((
    (t := time(h, m, s), int(times[t]) if t in times else 0)
    for h in range(24) for m in range(60) for s in range(60)
), columns=['Time', 'Counts'])
print(time_counts)

print(time_counts[time_counts['Time'] == time(13, 1, 2)])

This basically creates an additional DataFrame times based on the original data (assuming you don't even have a Time and Date column, but if you do, you can of course use those) - times takes all the times from df and then groups and counts them.

However, that is missing the times which don't occur in df, so time_counts is constructed by generated all possible times and either selecting the count from times or 0 if it doesn't exist in times.

Result:

           Time  Counts
0      00:00:00       0
1      00:00:01       0
2      00:00:02       0
3      00:00:03       0
4      00:00:04       0
...         ...     ...
86395  23:59:55       0
86396  23:59:56       0
86397  23:59:57       0
86398  23:59:58       0
86399  23:59:59       0

[86400 rows x 2 columns]
           Time  Counts
46862  13:01:02       2

User @riley's suggestion seems to point at a nicer solution, something like:

# create df as before, then:

df['Time'] = df['DateTime'].dt.time.astype('category')
result = df.value_counts('Time')

But that seems to have the same problem as you originally stated, even though the dtype of the 'Time' column is category. Perhaps someone has additional suggestions to make that work.