We can easily add new columns to an existing DataFrame using the indexing syntax:

dataframe[column_name] = values

It is important that if values is a list, it needs to have the same number of elements as there are rows in the DataFrame, otherwise you'll get an error. Alternatively, we can assign a single value to the entire new column as well.

Example 1: New Column from a Single Value


              1234567891011
            
import pandas as pd

df = pd.DataFrame({
    'Product': ['Laptop', 'Tablet', 'Phone'],
    'Old Price': [1000, 600, 400]
})

# Add a new column with a fixed price for all rows
df['New Price'] = 700

print(df)

Example 2: New Column using a List of Values


              1234567891011
            
import pandas as pd

df = pd.DataFrame({
    'Member': ['Sophie', 'Liam', 'Emma'],
    'Role': ['Designer', 'Developer', 'Tester']
})

# Add a new column for Project Name
df['Project'] = ['Marketing Website Redesign', 'Client Portal Backend Development', 'Payment Flow QA Testing']

print(df)

Example 3: New Column derived from Another Column


              1234567891011
            
import pandas as pd

df = pd.DataFrame({
    'Product': ['Laptop', 'Tablet', 'Phone'],
    'Price': [1000, 600, 400]
})

# Derive a new column 'Discounted Price' (10% off)
df['Discounted Price'] = df['Price'] * 0.9

print(df)

1. What happens if you try to add a new column to a DataFrame with a list that has fewer elements than the number of rows?

2. Which of the following lines correctly adds a column `Discount` which is 20% of the `Price`?

3. What would be the output of the following code?

Which of the following lines correctly adds a column Discount which is 20% of the Price?

Select the correct answer

df['Discount'] = df['Price'] - 0.2

df['Discount'] = df['Price'] * 20

df['Discount'] = df{Price} * 0.2

df['Discount'] = df['Price'] * 0.2

What would be the output of the following code?

Select the correct answer

       Item  Price  Final Price
0   Monitor    200        210.0
1  Keyboard     50         55.0
2     Mouse     25         27.5

       Item  Price  Final Price
0   Monitor    200       220.0
1  Keyboard     50        60.0
2     Mouse     25        30.0

       Item  Price  Final Price
0   Monitor    200       200.0
1  Keyboard     50        50.0
2     Mouse     25        25.0

       Item  Price  Final Price
0   Monitor    200        20.0
1  Keyboard     50         5.0
2     Mouse     25         2.5

War alles klar?

Danke für Ihr Feedback!

Abschnitt 2. Kapitel 5

Fragen Sie AI

Fragen Sie alles oder probieren Sie eine der vorgeschlagenen Fragen, um unser Gespräch zu beginnen

Suggested prompts:

Fragen Sie mich Fragen zu diesem Thema

Zusammenfassen Sie dieses Kapitel

Zeige reale Beispiele

Swipe um das Menü anzuzeigen

We can easily add new columns to an existing DataFrame using the indexing syntax:

dataframe[column_name] = values

Example 1: New Column from a Single Value


              1234567891011
            
import pandas as pd

df = pd.DataFrame({
    'Product': ['Laptop', 'Tablet', 'Phone'],
    'Old Price': [1000, 600, 400]
})

# Add a new column with a fixed price for all rows
df['New Price'] = 700

print(df)

Example 2: New Column using a List of Values


              1234567891011
            
import pandas as pd

df = pd.DataFrame({
    'Member': ['Sophie', 'Liam', 'Emma'],
    'Role': ['Designer', 'Developer', 'Tester']
})

# Add a new column for Project Name
df['Project'] = ['Marketing Website Redesign', 'Client Portal Backend Development', 'Payment Flow QA Testing']

print(df)

Example 3: New Column derived from Another Column


              1234567891011
            
import pandas as pd

df = pd.DataFrame({
    'Product': ['Laptop', 'Tablet', 'Phone'],
    'Price': [1000, 600, 400]
})

# Derive a new column 'Discounted Price' (10% off)
df['Discounted Price'] = df['Price'] * 0.9

print(df)

1. What happens if you try to add a new column to a DataFrame with a list that has fewer elements than the number of rows?

2. Which of the following lines correctly adds a column `Discount` which is 20% of the `Price`?

3. What would be the output of the following code?

Which of the following lines correctly adds a column Discount which is 20% of the Price?

Select the correct answer

df['Discount'] = df['Price'] - 0.2

df['Discount'] = df['Price'] * 20

df['Discount'] = df{Price} * 0.2

df['Discount'] = df['Price'] * 0.2

What would be the output of the following code?

Select the correct answer

       Item  Price  Final Price
0   Monitor    200        210.0
1  Keyboard     50         55.0
2     Mouse     25         27.5

       Item  Price  Final Price
0   Monitor    200       220.0
1  Keyboard     50        60.0
2     Mouse     25        30.0

       Item  Price  Final Price
0   Monitor    200       200.0
1  Keyboard     50        50.0
2     Mouse     25        25.0

       Item  Price  Final Price
0   Monitor    200        20.0
1  Keyboard     50         5.0
2     Mouse     25         2.5

War alles klar?

Danke für Ihr Feedback!

Abschnitt 2. Kapitel 5

Adding new Columns

Example 1: New Column from a Single Value

Example 2: New Column using a List of Values

Example 3: New Column derived from Another Column

1. What happens if you try to add a new column to a DataFrame with a list that has fewer elements than the number of rows?

2. Which of the following lines correctly adds a column `Discount` which is 20% of the `Price`?

3. What would be the output of the following code?

Awesome!

Adding new Columns

Example 1: New Column from a Single Value

Example 2: New Column using a List of Values

Example 3: New Column derived from Another Column

1. What happens if you try to add a new column to a DataFrame with a list that has fewer elements than the number of rows?

2. Which of the following lines correctly adds a column `Discount` which is 20% of the `Price`?

3. What would be the output of the following code?

Adding new Columns

Example 1: New Column from a Single Value

Example 2: New Column using a List of Values

Example 3: New Column derived from Another Column

1. What happens if you try to add a new column to a DataFrame with a list that has fewer elements than the number of rows?

2. Which of the following lines correctly adds a column Discount which is 20% of the Price?

3. What would be the output of the following code?

Awesome!

Adding new Columns

Example 1: New Column from a Single Value

Example 2: New Column using a List of Values

Example 3: New Column derived from Another Column

1. What happens if you try to add a new column to a DataFrame with a list that has fewer elements than the number of rows?

2. Which of the following lines correctly adds a column Discount which is 20% of the Price?

3. What would be the output of the following code?

2. Which of the following lines correctly adds a column `Discount` which is 20% of the `Price`?

2. Which of the following lines correctly adds a column `Discount` which is 20% of the `Price`?