The datetime type in pandas comes with a number of useful built-in functions to get additional information about the given date. In this tutorial, we will look at how to check if a date in a pandas dataframe is the first day of a month or not with the help of some examples.

## Using the `is_month_start`

attribute

You can use `is_month_start`

attribute on a pandas series (or a column in a dataframe) containing datetime values with the help the `.dt`

accessor to check if each date is the start date of a month or not.

The following is the syntax –

df["Date"].dt.is_month_start

It returns a boolean pandas series where `True`

represents that the corresponding date is the first date of the month and `False`

represents that it’s not.

## Examples

Let’s now look at some examples of using the above syntax.

First, we will create a sample dataframe to apply the above method.

import pandas as pd # create a dataframe df = pd.DataFrame({ "Date": pd.date_range("2023-03-01", "2023-03-10"), "Sales": [10, 12, 7, 17, 21, 5, 11, 13, 14, 8] }) # display the dataframe df

Output:

Here, we created a dataframe with the sales data for an ecommerce website for the first 10 days of March 2023. Notice, we used the pandas `date_range()`

function to get datetime values from “2023-03-01” to “2023-03-10” (both inclusive).

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Let’s now check whether the dates in the “Date” represent the first day of a month or not.

df["Date"].dt.is_month_start

Output:

0 True 1 False 2 False 3 False 4 False 5 False 6 False 7 False 8 False 9 False Name: Date, dtype: bool

We get a pandas series of boolean values.

Let’s add the result from the `is_month_start`

attribute as an additional column in the above dataframe.

# add new column df["Is First Day of Month"] = df["Date"].dt.is_month_start # display the dataframe df

Output:

You might also be interested in –

- Check if a DataFrame column is of datetime dtype in Pandas
- Get Rows using Datetime Index in Pandas
- Pandas – Add Days to Date (With Examples)
- Pandas – How to Create a date range?
- Pandas – Get only date from datetime
- Pandas – Get Month from Date

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