Data Transformation definition:
Data transformation in the context of data engineering refers to the process of converting, reshaping, or manipulating raw data into a structured and usable format.
Data transformation involves applying various operations such as filtering, aggregation, cleaning, and normalization to ensure that the data is consistent, accurate, and ready for analysis. Data transformation plays a crucial role in preparing data for storage, integration, and analysis, enabling organizations to derive valuable insights and make informed decisions from their data assets.
This said, data can be transformed at many different steps in a data pipeline. A key to success is to be able to track and observe any data transformation steps introduced in the process, and build that into the data lineage.
Data transformation approaches:
Transforming data on the fly (i.e., during the extraction or loading stage) can be more efficient and faster, as it avoids the need for a separate transformation layer. However, it can also be more complex and harder to maintain, especially as the volume and complexity of the data increase.
Using a transformation layer like dbt can provide several benefits. For example, it can simplify and centralize the transformation logic, making it easier to maintain, test, and audit. It can also provide features like version control, documentation, and collaboration tools. Additionally, dbt can help enforce data quality and consistency by providing automated data validation and testing.
In general, using a transformation layer like dbt can be a best practice for data processing pipelines, especially in larger and more complex environments. However, it's important to carefully evaluate the specific needs and trade-offs of your project to determine the best approach.
There are many Python functions that can be used for data transformation in data engineering. Some of the most frequently used ones include:
filter(): These functions can be used to transform and filter elements in a list or other iterable. For example,
map()can be used to apply a function to each element in a list, while
filter()can be used to remove elements from a list that do not meet a certain condition.
apply(): This function is part of the Pandas library and can be used to apply a function to each row or column of a DataFrame.
merge(): These functions can be used to combine data from multiple sources.
join()is used to combine data based on a common index, while
merge()can be used to combine data based on common columns.
groupby(): This function is also part of the Pandas library and can be used to group data by one or more columns and perform operations on each group.
agg(): This function is used with
groupby()and can be used to apply multiple aggregation functions to each group.
pivot_table(): This function is also part of the Pandas library and can be used to create a pivot table from a DataFrame.
join(): These functions can be used to split a string into a list and join a list into a string, respectively.
timedelta(): These functions can be used to work with dates and times in Python, such as converting a string to a datetime object or calculating the difference between two dates.
json.dumps(): These functions can be used to convert a JSON string to a Python object and vice versa.
numpy.reshape(): This function is part of the NumPy library and can be used to reshape an array into a new shape.