Append column to pandas dataframe

Append column to pandas dataframe

You can append a column to a Pandas DataFrame using several methods. Here, I'll show you two common approaches using the .assign() method and direct assignment.

Assuming you have a DataFrame called df and want to add a new column called "new_column" with some data:

  1. Using .assign() method:

    You can use the .assign() method to create a new DataFrame with the added column without modifying the original DataFrame:

    import pandas as pd # Create a DataFrame data = {'A': [1, 2, 3], 'B': [4, 5, 6]} df = pd.DataFrame(data) # Add a new column df = df.assign(new_column=[7, 8, 9]) print(df)

    This will create a new DataFrame df with the "new_column" added.

  2. Direct Assignment:

    You can also directly assign values to a new column in the existing DataFrame:

    import pandas as pd # Create a DataFrame data = {'A': [1, 2, 3], 'B': [4, 5, 6]} df = pd.DataFrame(data) # Add a new column df['new_column'] = [7, 8, 9] print(df)

    This will add the "new_column" to the existing DataFrame df.

Both of these methods will result in the same DataFrame with the new column appended. Choose the one that suits your workflow and coding style.

Examples

  1. "How to append a column to a pandas dataframe in Python?" Description: This query seeks a straightforward method to add a new column to an existing pandas dataframe using Python. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Append a new column df['C'] = [7, 8, 9] print(df)

  2. "Pandas dataframe append column example" Description: Users typically look for examples to understand how to append a column to a pandas dataframe. This query specifically targets such examples. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Create a new column new_column = [7, 8, 9] # Append the new column df['C'] = new_column print(df)

  3. "Python pandas add column to dataframe" Description: This query seeks a Pythonic approach to add a column to a pandas dataframe, indicating a preference for concise and efficient code. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Add a new column using assign method df = df.assign(C=[7, 8, 9]) print(df)

  4. "Appending data to pandas dataframe column" Description: Users might be interested in appending data to an existing column within a pandas dataframe, implying an intention to extend the existing values. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Define data to append new_data = [7, 8, 9] # Append data to an existing column df['C'] = df['C'].append(pd.Series(new_data), ignore_index=True) print(df)

  5. "Pandas dataframe insert column" Description: Sometimes, users may mistakenly use the term "append" instead of "insert" when referring to adding columns. This query addresses inserting columns into a pandas dataframe. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Insert a new column at index 1 df.insert(1, 'C', [7, 8, 9]) print(df)

  6. "How to add a column to a dataframe in pandas" Description: This query is a generic request for adding columns to pandas dataframes, likely from users new to pandas or Python. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Add a new column using dictionary assignment df['C'] = [7, 8, 9] print(df)

  7. "Appending multiple columns to pandas dataframe" Description: Some users may need to add multiple columns simultaneously to a pandas dataframe, hence the interest in appending multiple columns. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Define multiple columns to append new_columns = pd.DataFrame({'C': [7, 8, 9], 'D': [10, 11, 12]}) # Append multiple columns df = pd.concat([df, new_columns], axis=1) print(df)

  8. "Add column to pandas dataframe from another dataframe" Description: Users may need to add a column to a pandas dataframe by extracting data from another dataframe. Code:

    import pandas as pd # Sample dataframes df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) df2 = pd.DataFrame({'C': [7, 8, 9]}) # Add column from another dataframe df1['C'] = df2['C'] print(df1)

  9. "Pandas append column from list" Description: Users might want to append a column to a pandas dataframe from a list of values, which could be a common scenario. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # List of values for the new column new_column = [7, 8, 9] # Append column from list df['C'] = new_column print(df)

  10. "Appending series to pandas dataframe as column" Description: Users may seek a method to append a pandas series as a new column to an existing dataframe. Code:

    import pandas as pd # Sample dataframe df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}) # Series to append new_series = pd.Series([7, 8, 9]) # Append series as column df['C'] = new_series print(df)

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