Python Pandas - Indicate whether the date in DateTimeIndex is the first day of the month

To check whether the date in DateTimeIndex is the first day of the month, use the DateTimeIndex.is_month_start property.

At first, import the required libraries −

import pandas as pd

Create a DatetimeIndex with period 6 and frequency as D i.e. days. The timezone is Australia/Adelaide −

datetimeindex = pd.date_range('2021-9-21 02:30:50', periods=6, tz='Australia/Adelaide', freq='5D')

Display DateTimeIndex −

print("DateTimeIndex...\n", datetimeindex)

Check whether the date in DateTimeIndex is the first day of the month −

print("\nCheck whether the date in DateTimeIndex is the first day of the month...\n",
datetimeindex.is_month_start)

Example

Following is the code −

import pandas as pd

# DatetimeIndex with period 6 and frequency as D i.e. days
# The timezone is Australia/Adelaide
datetimeindex = pd.date_range('2021-9-21 02:30:50', periods=6, tz='Australia/Adelaide', freq='5D')

# display DateTimeIndex
print("DateTimeIndex...\n", datetimeindex)

# display DateTimeIndex frequency
print("DateTimeIndex frequency...\n", datetimeindex.freq)

# Check whether the date in DateTimeIndex is the first day of the month
print("\nCheck whether the date in DateTimeIndex is the first day of the month...\n",
datetimeindex.is_month_start)

Output

This will produce the following code −

DateTimeIndex...
DatetimeIndex(['2021-09-21 02:30:50+09:30', '2021-09-26 02:30:50+09:30',
'2021-10-01 02:30:50+09:30', '2021-10-06 02:30:50+10:30',
'2021-10-11 02:30:50+10:30', '2021-10-16 02:30:50+10:30'],
dtype='datetime64[ns, Australia/Adelaide]', freq='5D')
DateTimeIndex frequency...
<5 * Days>

Check whether the date in DateTimeIndex is the first day of the month...
[False False True False False False]