在Python中按小时分组，而不添加不存在的小时

import datetime
import pandas as pd

timestamps = [
    "2022-01-01 10:15:30",
    "2022-01-01 11:20:45",
    "2022-01-02 09:30:00",
    "2022-01-02 10:45:15",
    "2022-01-02 12:00:00"
]

datetimes = [datetime.datetime.strptime(ts, "%Y-%m-%d %H:%M:%S") for ts in timestamps]
hours = [dt.hour for dt in datetimes]

df = pd.DataFrame({"timestamp": timestamps, "hour": hours})
grouped = df.groupby("hour").size()

for hour, count in grouped.items():
    print(f"Hour {hour}: {count} occurrences")