In this posts, you’ll learn how to transpose a Pandas dataframe using both the `.T`

attribute and the `.transpose()`

method. Additionally, you’ll learn how to create a copy of the dataframe (rather than a view representation).

Table of Contents

## Loading a Sample Dataframe

For this tutorial, we’ll be using two different dataframes. This is because the `.transpose()`

method works differently, depending on whether your dataframe has mixed datatypes or not.

Let’s get started by loading some sample dataframes:

import pandas as pd df1 = pd.DataFrame.from_dict( { 'Name': ['Jane', 'Melissa', 'John', 'Matt'], 'Age': [23, 45, 35, 64], 'Birth City': ['London', 'Paris', 'Toronto', 'Atlanta'], 'Gender': ['F', 'F', 'M', 'M'] } ) df2 = pd.DataFrame.from_dict( { 'Age': [1,2,3,4,5], 'Size': [10,24,43,54,56] } ) print('Dataframe df1:') print(df1) print('Dataframe df2:') print(df2)

This returns the following:

Dataframe df1: Name Age Birth City Gender 0 Jane 23 London F 1 Melissa 45 Paris F 2 John 35 Toronto M 3 Matt 64 Atlanta M Dataframe df2: Age Size 0 1 10 1 2 24 2 3 43 3 4 54 4 5 56

## What is Transposing?

In linear algebra, and, thereby, in machine learning, transposing a matrix involves switching the rows and columns of a matrix. This operation is often used to estimate variances and covariances in regression.

A transposed matrix, say `df`

, is often denoted as `df^T`

.

By switching the rows and columns of a matrix, the shape of a matrix is altered. This is unless the rows and columns have the same dimensions, in which case the matrix size remains the same.

For example, say you have a matrix with 3 rows and 2 columns. The transpose of this matrix would have 2 rows and 3 columns.

Learn more about transposing by checking out this wikipedia entry on it.

## Transposing a Pandas Dataframe

Pandas has two easy ways to transpose a dataframe. You can do this either be appending `.T`

to the end of a dataframe, or by calling the `.transpose()`

method (which gives you a bit more flexibility by adding parameters to it).

Let’s transpose the dataframe `df2`

and we’ll explore its transpose a little bit before we dive into a more complicated transpose after.

Let’s use the `.T`

method of transposing our dataframe:

>>> df2_T = df2.T >>> print(df2_T) 0 1 2 3 4 Age 1 2 3 4 5 Size 10 24 43 54 56

Now, it’s important here to note that all of our values have the same datatype (integers, to be specific). Let’s explore the data types of the original dataframe as well as its transpose:

df2_T = df2.T print('df2\'s datatypes:') print(df2.dtypes) print('\n') print('df2_T\'s datatypes:') print(df2_T.dtypes)

This returns the following information:

df2's datatypes: Age int64 Size int64 dtype: object df2_T's datatypes: 0 int64 1 int64 2 int64 3 int64 4 int64 dtype: object

Check out some other Python tutorials on datagy, including our complete guide to styling Pandas and our comprehensive overview of Pivot Tables in Pandas!

### Transposing a Pandas Dataframe with Mixed Data Types

We can see here in both the original dataframe and in the transpose that all the datatypes are `int64`

.

Now let’s explore what happens with mixed data types, as found in `df_1`

.

df1_T = df1.transpose() print(df1_T)

This returns the following:

0 1 2 3 Name Jane Melissa John Matt Age 23 45 35 64 Birth City London Paris Toronto Atlanta Gender F F M M

If we now look at the data types of these two dataframes we can see the following items are returned:

df1_T = df1.T print('df1\'s datatypes:') print(df1.dtypes) print('\n') print('df1_T\'s datatypes:') print(df1_T.dtypes)

Which returns:

df1's datatypes: Name object Age int64 Birth City object Gender object dtype: object df1_T's datatypes: 0 object 1 object 2 object 3 object dtype: object

We can see any new column that has `mixed`

data types are immediately assigned `object`

as their new data type. Keep this in mind if you’re hoping to perform some types of calculations on these columns.

## Create a Transpose Copy for Mixed Datatypes

By default, Pandas will create a copy of the dataframe if there are mixed data types. This is handled implicitly when Pandas identifies mixed data types allowing you to make this change happen automatically.

That being said, should you have the same data type throughout, as in our `df2`

example, you can explicitly tell Pandas to generate a copy by setting `copy=True`

.

## Conclusion

In this post, you learned how to transpose a Pandas dataframe. You learned how to do this using both `.T`

and the `.transpose()`

method. You also learned a little bit about what transposing actually is, and how different data types may impact your results.

To learn more about the Pandas transpose function, check out the official documentation here.