In this tutorial, we will look at how to convert a category type column in Pandas to a list with the help of some examples.
How to get the list of values from a Pandas categorical column?
You can use the Pandas series tolist()
or the Python built-in list()
function to get values from a Pandas column as a list. This method works for category
type columns as well. The following is the syntax –
# using pandas series .tolist() df["Col"].tolist() # using python list() list(df["Col"])
We get the column values as a list in the order they appear in the dataframe.
Examples
Let’s look at the usage of the above methods with the help of some examples. First, we’ll create a sample Pandas dataframe that we’ll be using throughout this tutorial.
import pandas as pd # create a dataframe df = pd.DataFrame({ "Name": ["Tim", "Sarah", "Hasan", "Jyoti", "Jack"], "Shirt Size": ["Small", "Medium", "Large", "Small", "Large"] }) # change to category dtype df["Shirt Size"] = df["Shirt Size"].astype("category") # display the dataframe print(df)
Output:
Name Shirt Size 0 Tim Small 1 Sarah Medium 2 Hasan Large 3 Jyoti Small 4 Jack Large
We now have a dataframe containing the name and the respective t-shirt size of some students participating in a university competition.
Note that the “Shirt Size” column is of category
type.
Category column to list
Let’s get the list of values in the “Shirt Size” column. We’ll use both the methods mentioned above. First, using the Pandas series tolist()
function and then, the Python built-in list()
function.
# "Shirt Size" column to list using tolist() print(df["Shirt Size"].tolist()) # "Shirt Size" column to list using list() print(list(df["Shirt Size"]))
Output:
['Small', 'Medium', 'Large', 'Small', 'Large'] ['Small', 'Medium', 'Large', 'Small', 'Large']
You can see that we get the same results from both the methods, that is, values in the “Shirt Size” column as a list.
Get all possible category values for a categorical column
If, on the other hand, you want to get the list of the possible category values for a categorical column, use the .categories
property with the help of the .cat
accessor.
Let’s get the allowed category values in the “Shirt Size” column.
# categories for "Shirt Size" column print(df["Shirt Size"].cat.categories)
Output:
Index(['Large', 'Medium', 'Small'], dtype='object')
You can see that we get the possible categories for the “Shirt Size” column. To convert to above result to a list, use the Python list()
function.
For more, refer to our tutorial on – Get List of Categories in Pandas Category Column
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