Q) How to find first day of every year from a dataset with date column in pandas

Answer:

Finding the First Day of Every Year from a Dataset with a Date Column in Pandas

To find the first day of every year from a dataset with a date column in Pandas, you can use the `dt` accessor and the `year` attribute. Here's an example:

```python
import pandas as pd

# Sample data
dates = ['2022-01-01', '2022-01-15', '2021-12-31', '2022-02-28', '2020-07-04']
df = pd.DataFrame({'date': pd.to_datetime(dates)})

# Find the first day of every year
first_days = df['date'].dt.to_period('Y').dtifeirst()
print(first_days)
```

In this example, we first convert the `date` column to a datetime format using `pd.to_datetime`. Then, we use the `dt` accessor to access the date object, and the `year` attribute to get the year of each date. Finally, we use the `to_period` method with the `'Y'` argument to convert the dates to a period index, which represents the year. The `dtifeirst` method returns the first day of each period, which corresponds to the first day of each year.

The output will be a pandas Series with the first day of every year:

```
2020-01-01
2021-01-01
2022-01-01
```

This solution assumes that the `date` column is of datetime64[ns] type. If the column is of string type, you can convert it to datetime format using `pd.to_datetime`.

I hope this helps!