This article will discuss different ways to get the last value a column in a Pandas Dataframe. In all of the solutions, we will first select the Column by either column name or index position; then, we will see different techniques to get and set the last value of that Column.
Table of Contents
- Get the last value of a column based on the column name
- Get the last value of a column based on column index position.
A DataFrame is a data structure offered by the Pandas module in Python. It stores the data in tabular format, i.e., in rows and columns. Let’s create a DataFrame from a list of tuples,
import pandas as pd
# List of Tuples
students = [('Mark', 24, 'Berlin', 'Germany', 89000),
('Rita', 20, 'Seoul', 'South Korea', 93000),
('Vicki', 21, 'Amsterdam', 'Netherlands', 95670),
('Justin', 22, 'Singapore', 'Singapore', 78900),
('John', 36, 'Paris', 'France', 98711),
('Michal', 37, 'London', 'United Kingdom', 90000)]
# Create a DataFrame object
df = pd.DataFrame( students,
columns=['Name', 'Age', 'City', 'Country', 'Budget'],
index=['a', 'b', 'c', 'd', 'e', 'f'])
print(df)
Output
Name Age City Country Budget a Mark 24 Berlin Germany 89000 b Rita 20 Seoul South Korea 93000 c Vicki 21 Amsterdam Netherlands 95670 d Justin 22 Singapore Singapore 78900 e John 36 Paris France 98711 f Michal 37 London United Kingdom 90000
Now let’s see how to get the last value of a specific column of this DataFrame,
Get the last value of a column based on the column name
Suppose we know the name of the column and want to fetch the last value of that Column. We can do that using two techniques. Let’s see them one by one,
Get the last value of a column using iat[]
First of all, select the Column of the DataFrame as a Series object, using the column name. Then call the iat[-1] attribute on that Series object to get the last value of that Column. For example,
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# Get last value of column 'City' last_value = df['City'].iat[-1] print(last_value)
Output:
London
Here we fetched the last value of the column ‘City’ from the DataFrame. As Series supports the negative indexing, therefore the iat[-1] returns the reference of the last value of the Series. We can use this to change the last value of the Column too. For example,
# Change the Last value of column 'City' df['City'].iat[-1] = 'Liverpool' # Display the DataFrame print(df)
Output:
Name Age City Country Budget a Mark 24 Berlin Germany 89000 b Rita 20 Seoul South Korea 93000 c Vicki 21 Amsterdam Netherlands 95670 d Justin 22 Singapore Singapore 78900 e John 36 Paris France 98711 f Michal 37 Liverpool United Kingdom 90000
Here, we changed the last value of column ‘City’ to Liverpool.
Get the last value of a column using iloc[]
In Pandas, the DataFrame provides a property iloc[]. In the iloc[row_number, column_number], we need to pass the row and column index positions, and it fetches the cell value based on that. But we have the column name instead of the column index position. So we need to get the column index from the column name using the get_loc() function and then use the iloc[] property with row value -1 to get the last value of the Column (because of negative indexing -1 denotes the last entry in the Series). For example,
import pandas as pd
# List of Tuples
students = [('Mark', 24, 'Berlin', 'Germany', 89000),
('Rita', 20, 'Seoul', 'South Korea', 93000),
('Vicki', 21, 'Amsterdam', 'Netherlands', 95670),
('Justin', 22, 'Singapore', 'Singapore', 78900),
('John', 36, 'Paris', 'France', 98711),
('Michal', 37, 'London', 'United Kingdom', 90000)]
# Create a DataFrame object
df = pd.DataFrame( students,
columns=['Name', 'Age', 'City', 'Country', 'Budget'],
index=['a', 'b', 'c', 'd', 'e', 'f'])
print(df)
# Get last value of column 'City'
last_value = df.iloc[-1, df.columns.get_loc('City')]
print(last_value)
Output:
Name Age City Country Budget a Mark 24 Berlin Germany 89000 b Rita 20 Seoul South Korea 93000 c Vicki 21 Amsterdam Netherlands 95670 d Justin 22 Singapore Singapore 78900 e John 36 Paris France 98711 f Michal 37 London United Kingdom 90000 London
Here we fetched the last value of the column ‘City’ from the DataFrame.
Using the get_loc() function, we last fetched the column number from column name and then passed that to iloc[] property of the DataFrame with row value -1. The iloc[], returned the reference of the last value of the Column. We can use this to change the last value of the Column too. For example,
# Change the Last value of column 'City'
df.iloc[-1, df.columns.get_loc('City')] = 'Birmingham'
# Display the DataFrame
print(df)
Output:
Name Age City Country Budget a Mark 24 Berlin Germany 89000 b Rita 20 Seoul South Korea 93000 c Vicki 21 Amsterdam Netherlands 95670 d Justin 22 Singapore Singapore 78900 e John 36 Paris France 98711 f Michal 37 Birmingham United Kingdom 90000
Here, we changed the last value of column ‘City’ to Birmingham.
Get the last value of a column based on column index position
In Pandas, the DataFrame provides a property iloc[]. In the iloc[row_number, column_number], we need to pass the row and column index positions, and it fetches the cell value based on that. As we already have the column index position, we can directly use that and pass -1 as the row number (negative indexing) to get the last value of the Column. For example,
import pandas as pd
# List of Tuples
students = [('Mark', 24, 'Berlin', 'Germany', 89000),
('Rita', 20, 'Seoul', 'South Korea', 93000),
('Vicki', 21, 'Amsterdam', 'Netherlands', 95670),
('Justin', 22, 'Singapore', 'Singapore', 78900),
('John', 36, 'Paris', 'France', 98711),
('Michal', 37, 'London', 'United Kingdom', 90000)]
# Create a DataFrame object
df = pd.DataFrame( students,
columns=['Name', 'Age', 'City', 'Country', 'Budget'],
index=['a', 'b', 'c', 'd', 'e', 'f'])
print(df)
column_index = 2
# Get last value of column index 2
last_value = df.iloc[-1, column_index]
print(last_value)
Output:
Name Age City Country Budget a Mark 24 Berlin Germany 89000 b Rita 20 Seoul South Korea 93000 c Vicki 21 Amsterdam Netherlands 95670 d Justin 22 Singapore Singapore 78900 e John 36 Paris France 98711 f Michal 37 London United Kingdom 90000 London
Here we fetched the last value of the column ‘City’ from the DataFrame. The iloc[] returns the reference of the last value of the Column. We can use this to change the last value of the Column too. For example,
column_index = 2 # Change the Last value of column index 2 df.iloc[-1, column_index] = 'Sheffield' # Display the DataFrame print(df)
Output:
Name Age City Country Budget a Mark 24 Berlin Germany 89000 b Rita 20 Seoul South Korea 93000 c Vicki 21 Amsterdam Netherlands 95670 d Justin 22 Singapore Singapore 78900 e John 36 Paris France 98711 f Michal 37 Sheffield United Kingdom 90000
Here, we changed the last value of column ‘City’ to Sheffield.
Summary
We learned about different ways to get and set a column’s last value, either by column name or index position.