How to write Pandas column values to a list?

This quick tutorial will cover the topic of writing a DataFrame column to a Python list.

Consider the following code snippet:

# import the pandas package
import pandas as pd

# initialize the DataFrame
data = pd.DataFrame({ "manager": ["Debbie", "Daisy", "Dorothy", "Tim"] * 2,
                     "target": [32000, 45000, 18000, 20000] * 2})
data.head()

Here’s our DataFrame header:

	manager	target
0	Debbie	32000
1	Daisy	45000
2	Dorothy	18000
3	Tim	20000
4	Debbie	32000

Using pd.DataFrame.tolist() to write column to a list

Here’s the Python code you’ll need to export column values to a Python list:

# Dataframe Column values to Python list
data['manager'].values.tolist()

Here’s the list object we’ll get:

[‘Debbie’, ‘Daisy’, ‘Dorothy’, ‘Tim’, ‘Debbie’, ‘Daisy’, ‘Dorothy’, ‘Tim’]

Pandas column index to list

data['manager'].index.tolist()

[0, 1, 2, 3, 4, 5, 6, 7]

Unique column values to list

As shown above, we were able to export the values to a list. The list however had duplicated entries. Here’s how to ensure that the list has only unique values:

# Export unique column values only
data['manager'].unique().tolist()

[‘Debbie’, ‘Daisy’, ‘Dorothy’, ‘Tim’]

Unique list values using set

Other way to ensure uniqueness in the list is to convert it to a set to get rid of duplicated values.

unique_managers = set(data['manager'].values.tolist())
list(unique_managers)

tolist() with condition

What if we just want to write values that satisfy a condition?

# Condition: Only managers which name starts with the letter D
cond = data['manager'].str.startswith('D')
data[cond]['manager'].unique().tolist()

Here’s the result:

[‘Debbie’, ‘Daisy’, ‘Dorothy’]

Series values to List

For completeness, here’s a short snippet for writing Series values to a list (you can find a more complete example here)

manager_series = pd.Series(["Debbie", "Kim", "Dorothy", "Tim"])
manager_series.to_list()

How to export a Python Dataframe column to a list?