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Appending a list to a Pandas DataFrame is done by using the DataFrame.append() method. This method takes in a list as an argument and returns a DataFrame with the list appended to the existing DataFrame. It is important to note that the append() method adds the list to the end of the DataFrame, making sure that all the index values are in the correct order. This method is useful for adding data from a list to a DataFrame in a structured and efficient manner.
You can use the following basic syntax to append a list to a pandas DataFrame:
#define list new_list = ['value1', 'value2', value3, value4] #append list to DataFrame df.loc[len(df)] = new_list
The following example shows how to use this syntax in practice.
Example: Append List to Pandas DataFrame
Suppose we have the following pandas DataFrame that contains information about various basketball teams:
import pandas as pd #create DataFrame df = pd.DataFrame({'team': ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I'], 'points': [18, 22, 19, 14, 14, 11, 20, 28, 22], 'assists': [5, 7, 7, 9, 12, 9, 9, 4, 8], 'rebounds': [11, 8, 10, 6, 6, 5, 9, 12, 9]}) #view DataFrame df team points assists rebounds 0 A 18 5 11 1 B 22 7 8 2 C 19 7 10 3 D 14 9 6 4 E 14 12 6 5 F 11 9 5 6 G 20 9 9 7 H 28 4 12 8 I 22 8 9
We can use the following code to append a list that contains information about a new basketball team to the end of the DataFrame:
#define list of values
new_team = ['J', 30, 10, 12]
#append list to DataFrame
df.loc[len(df)] = new_team
#view updated DataFrame
df
team points assists rebounds
0 A 18 5 11
1 B 22 7 8
2 C 19 7 10
3 D 14 9 6
4 E 14 12 6
5 F 11 9 5
6 G 20 9 9
7 H 28 4 12
8 I 22 8 9
9 J 30 10 12
Notice that the list of values has been appended as a new row to the end of the DataFrame.
Note that you’ll receive an error if the number of values in the list does not match the number of columns in the existing DataFrame.
For example, suppose we attempt to append the following list to the end of the DataFrame:
#define list of values
new_team = ['J', 30]
#append list to DataFrame
df.loc[len(df)] = new_team
#view updated DataFrame
df
ValueError: cannot set a row with mismatched columns
We receive an error because our list contains two values, but the existing pandas DataFrame contains four columns.
To append a list to the end of this DataFrame, the list must also contain four values.