Convert Year-Month Strings to a Timeseries With Consistent Day Number

mubashir_rizvi · March 18, 2023, 6:04pm

When working with time-series data, it’s common to encounter year-month strings that need to be converted to dates. And often, it’s necessary to ensure that the resulting dates have a consistent or same-day number, such as the 4th day of every chosen month. In this thread, you’ll learn different ways how you can accomplish the task of converting such strings into a time series having a consistent day number. If you want to learn how you can simply convert string dates into time series dates, check out the thread of Creating a timeseries from a series of date-strings.

1. Using Pandas "to_datetime()" method:

The to_datetime() function in Pandas is used to convert an input series or list of date-like objects to a Pandas DatetimeIndex object.
In this method, to_datetime() is used to convert the year-month string series to a DatetimeIndex object, and the year-month strings are concatenated with -04 to ensure that each resulting date has the same day number.

2. Using NumPy's "np.datetime64()" method:

To create a date-time object from a string, integer, or other input, the np.datetime64() function is utilized.
In the provided example code, this function is applied on a series using the apply() method, which is designed to apply any function to a series or dataframe object.
The specific purpose of np.datetime64() in this example is to concatenate -04 to each element in the series and convert it into a date-time object

3. Using datetime's "strptime()" method:

The datetime module in Python provides classes for working with dates and times. It provides functions for parsing, formatting, and manipulating dates and times. In this method, class datetime is used which is used to represent both date and time.
The strptime() is a method of the datetime class and is used to parse a string representation of a date and time using a specified format string. In this case, strptime() is used to parse each year-month string in the series, concatenate -04 to each element in it, and return a date-time series object.
This method is incorporated in a simple lambda function which is applied to each element of the series using the apply() function.

4. Using "arrow" library:

The Arrow library is a Python library used for working with dates and times, similar to the datetime module in Python’s standard library.
The arrow.get() method is used to parse a string representation of a date and time using a specified format string.
In this case, get() is used to parse each year-month string in the series, concatenate -04 to each element in the series, and return an Arrow object for that month with the day number set to 4.
The method get() is used in a simple lambda function which is applied to each element of the series using the apply() method.