Python Pandas: How to Swap Two DataFrame Columns

Reordering columns in a Pandas DataFrame is a common data manipulation task, often needed for presentation, analysis, or preparing data for specific models. You might want to swap the positions of two specific columns or define a completely new column order.

This guide explains several methods to swap two DataFrame columns in Pandas, covering scenarios where you want to swap only their positions or swap both their names and underlying data.

Understanding Column Swapping: Position vs. Name/Content

It's crucial to distinguish between:

• Swapping Column Positions: Changing the display order of columns while keeping their names and data associated. For example, if you have columns A, B, C, you might want A, C, B. The data within column B remains with column B, it just moves. This is the most common interpretation of "swapping columns."
• Swapping Column Names and Content (Effectively Renaming and Reassigning): This is less common for a simple "swap" operation. It would mean if column B had data X and column C had data Y, after the swap, the column now named C would have data X, and the column now named B would have data Y. This is more akin to renaming columns and potentially reassigning their data, which df.columns = new_names_list can achieve if new_names_list is a permutation of the old names. This article primarily focuses on swapping column positions.

Example DataFrame:

import pandas as pd

data = {
    'ID': [101, 102, 103, 104],
    'Name': ['Alice', 'Bob', 'Charlie', 'David'],
    'Department': ['HR', 'Engineering', 'HR', 'Sales'],
    'StartDate': ['2020-01-15', '2019-03-01', '2021-06-10', '2020-08-20'],
    'Salary': [60000, 85000, 62000, 70000]
}
df_original = pd.DataFrame(data)
print("Original DataFrame:")
print(df_original)

Output:

Original DataFrame:
    ID     Name   Department   StartDate  Salary
0  101    Alice           HR  2020-01-15   60000
1  102      Bob  Engineering  2019-03-01   85000
2  103  Charlie           HR  2021-06-10   62000
3  104    David        Sales  2020-08-20   70000

Method 1: Reordering by Providing a New Column List (Swaps Positions)

This is the standard way to change the order of columns, including swapping two specific ones. You create a new list representing the desired order of column names and then reindex or select the DataFrame columns based on this new list.

Using DataFrame.reindex(columns=...)

The reindex() method can conform the DataFrame to a new set of column labels.

import pandas as pd

data = {
    'ID': [101, 102, 103, 104],
    'Name': ['Alice', 'Bob', 'Charlie', 'David'],
    'Department': ['HR', 'Engineering', 'HR', 'Sales'],
    'StartDate': ['2020-01-15', '2019-03-01', '2021-06-10', '2020-08-20'],
    'Salary': [60000, 85000, 62000, 70000]
}

df_original = pd.DataFrame(data)

df = df_original.copy() # Work on a copy

# Original columns: ['ID', 'Name', 'Department', 'StartDate', 'Salary']
# Let's swap 'Department' and 'StartDate'
new_column_order = ['ID', 'Name', 'StartDate', 'Department', 'Salary']

df_reindexed = df.reindex(columns=new_column_order)

print("DataFrame after reindex (Department and StartDate swapped):")
print(df_reindexed)

Output:

DataFrame after reindex (Department and StartDate swapped):
    ID     Name   StartDate   Department  Salary
0  101    Alice  2020-01-15           HR   60000
1  102      Bob  2019-03-01  Engineering   85000
2  103  Charlie  2021-06-10           HR   62000
3  104    David  2020-08-20        Sales   70000

• The columns argument in reindex specifies the new order.

Using DataFrame.loc[:, new_column_list] or df[new_column_list]

You can also use standard DataFrame indexing by passing the new list of column names.

import pandas as pd

data = {
    'ID': [101, 102, 103, 104],
    'Name': ['Alice', 'Bob', 'Charlie', 'David'],
    'Department': ['HR', 'Engineering', 'HR', 'Sales'],
    'StartDate': ['2020-01-15', '2019-03-01', '2021-06-10', '2020-08-20'],
    'Salary': [60000, 85000, 62000, 70000]
}

df_original = pd.DataFrame(data)

df = df_original.copy()

new_column_order = ['ID', 'Name', 'StartDate', 'Department', 'Salary']

# Using df[new_column_order]
df_bracket_selection = df[new_column_order]
print("DataFrame after bracket selection (Department and StartDate swapped):")
print(df_bracket_selection)

# Using df.loc[:, new_column_order] (more explicit)
df_loc_selection = df.loc[:, new_column_order]
print("DataFrame after .loc selection (Department and StartDate swapped):")
print(df_loc_selection)

Output:

DataFrame after bracket selection (Department and StartDate swapped):
    ID     Name   StartDate   Department  Salary
0  101    Alice  2020-01-15           HR   60000
1  102      Bob  2019-03-01  Engineering   85000
2  103  Charlie  2021-06-10           HR   62000
3  104    David  2020-08-20        Sales   70000
DataFrame after .loc selection (Department and StartDate swapped):
    ID     Name   StartDate   Department  Salary
0  101    Alice  2020-01-15           HR   60000
1  102      Bob  2019-03-01  Engineering   85000
2  103  Charlie  2021-06-10           HR   62000
3  104    David  2020-08-20        Sales   70000

note

Both df[new_column_order] and df.loc[:, new_column_order] achieve the same result of reordering columns based on the provided list.

Creating the New Column List

To swap two specific columns, say col_A and col_B, while keeping others in place:

1. Get the current list of column names.
2. Find the indices of col_A and col_B.
3. Swap these names in the list.

import pandas as pd

data = {
    'ID': [101, 102, 103, 104],
    'Name': ['Alice', 'Bob', 'Charlie', 'David'],
    'Department': ['HR', 'Engineering', 'HR', 'Sales'],
    'StartDate': ['2020-01-15', '2019-03-01', '2021-06-10', '2020-08-20'],
    'Salary': [60000, 85000, 62000, 70000]
}

df_original = pd.DataFrame(data)

df = df_original.copy()

cols_to_swap = ['Department', 'Salary']
col1_name, col2_name = cols_to_swap[0], cols_to_swap[1]

current_columns = list(df.columns) # Get list of current column names
print(f"Original column order: {current_columns}")

# Find indices of the columns to swap
idx1 = current_columns.index(col1_name)
idx2 = current_columns.index(col2_name)

# Swap the names in the list
current_columns[idx1], current_columns[idx2] = current_columns[idx2], current_columns[idx1]
swapped_column_order = current_columns
print(f"New column order after swapping '{col1_name}' and '{col2_name}': {swapped_column_order}")

# Apply the new order
df_swapped_specific = df[swapped_column_order]
print("\nDataFrame with specific columns swapped:")
print(df_swapped_specific)

Output:

Original column order: ['ID', 'Name', 'Department', 'StartDate', 'Salary']
New column order after swapping 'Department' and 'Salary': ['ID', 'Name', 'Salary', 'StartDate', 'Department']

DataFrame with specific columns swapped:
    ID     Name  Salary   StartDate   Department
0  101    Alice   60000  2020-01-15           HR
1  102      Bob   85000  2019-03-01  Engineering
2  103  Charlie   62000  2021-06-10           HR
3  104    David   70000  2020-08-20        Sales

Method 2: Swapping Column Names and Content (Rename-like behavior)

If the goal is not just to change the display order but to effectively swap the names associated with the data of two columns, this is more like a renaming operation where the data under the old names effectively moves to the new names. A direct assignment to df.columns achieves this if the new list of names is a permutation.

Using df.columns Assignment

This method directly reassigns the columns attribute of the DataFrame. If you provide a list of column names that is a permutation of the original (e.g., two names swapped), Pandas will reassign the names. The underlying data itself doesn't move; the labels pointing to the data series are what change.

import pandas as pd

data_for_rename = {
    'Col_X': [1, 2, 3],
    'Col_Y': ['A', 'B', 'C'],
    'Col_Z': [True, False, True]
}
df_rename = pd.DataFrame(data_for_rename)
print("Original DataFrame for renaming:")
print(df_rename)

# Original columns: ['Col_X', 'Col_Y', 'Col_Z']
# We want the data under 'Col_X' to now be under 'Col_Y_NewName',
# and data under 'Col_Y' to be under 'Col_X_NewName'.
# This is NOT a simple positional swap, but a relabeling.

# To truly swap contents AND names:
# Step 1: Create the desired new order of NAMES
cols = list(df_rename.columns)
idx_x = cols.index('Col_X')
idx_y = cols.index('Col_Y')
cols[idx_x], cols[idx_y] = cols[idx_y], cols[idx_x] # Swap names in list: ['Col_Y', 'Col_X', 'Col_Z']

# Step 2: Assign these new names to the DataFrame's columns attribute
df_rename.columns = cols
print("\nDataFrame after swapping names via df.columns = ...:")
print(df_rename)

Output:

Original DataFrame for renaming:
   Col_X Col_Y  Col_Z
0      1     A   True
1      2     B  False
2      3     C   True

DataFrame after swapping names via df.columns = ...:
   Col_Y Col_X  Col_Z
0      1     A   True
1      2     B  False
2      3     C   True

note

Important Distinction: Using df.columns = new_list_of_names re-labels the existing series of data. If new_list_of_names is just a reordering of the original names, it looks like the columns and their data have swapped positions. If new_list_of_names contains different names, it's a rename. This is fundamentally different from Method 1, where df.reindex(columns=...) or df[new_order] selects and reorders existing named columns along with their data.

Creating a Reusable Function to Swap Two Columns (Positions)

For convenience, especially when swapping two specific columns by name: this function swap_columns_by_name() safely creates a list of current column names, finds the indices of the two columns to be swapped, swaps their names in the list, and then re-selects the DataFrame columns in this new order.

import pandas as pd

def swap_columns_by_name(df_input, col_name1, col_name2):
  """Swaps the positions of two columns in a DataFrame by their names."""
  df = df_input.copy() # Work on a copy to avoid modifying original DataFrame
  column_list = list(df.columns)

  try:
    idx1 = column_list.index(col_name1)
    idx2 = column_list.index(col_name2)
  except ValueError:
    print(f"Error: One or both column names ('{col_name1}', '{col_name2}') not found in DataFrame.")
    return df_input # Return original if columns not found

  # Swap the names in the list
  column_list[idx1], column_list[idx2] = column_list[idx2], column_list[idx1]

  # Return DataFrame with reordered columns
  return df[column_list]


data = {
    'ID': [101, 102, 103, 104],
    'Name': ['Alice', 'Bob', 'Charlie', 'David'],
    'Department': ['HR', 'Engineering', 'HR', 'Sales'],
    'StartDate': ['2020-01-15', '2019-03-01', '2021-06-10', '2020-08-20'],
    'Salary': [60000, 85000, 62000, 70000]
}

df_original = pd.DataFrame(data)
df = df_original.copy()

df_swapped_func = swap_columns_by_name(df, 'Department', 'Salary')
print("DataFrame after swapping 'Department' and 'Salary' using function:")
print(df_swapped_func.head()) # .head() for brevity if needed

Output:

DataFrame after swapping 'Department' and 'Salary' using function:
    ID     Name  Salary   StartDate   Department
0  101    Alice   60000  2020-01-15           HR
1  102      Bob   85000  2019-03-01  Engineering
2  103  Charlie   62000  2021-06-10           HR
3  104    David   70000  2020-08-20        Sales

Conclusion

To swap the positions of columns in a Pandas DataFrame:

1. Create a list of column names in the new desired order.
2. Use this list to reindex or select columns:
   • df_new = df.reindex(columns=new_order_list)
   • df_new = df[new_order_list] (or df.loc[:, new_order_list]) (Most common)

If you need to swap columns by name programmatically, create a function that manipulates the list of column names and then applies this new order.

Assigning directly to df.columns = new_name_list primarily re-labels the columns. If the new_name_list is a permutation of the old names, it effectively swaps the names associated with the underlying data series, which can appear as a content swap if you track by name. For simply changing the display order of existing named columns, reindexing with a new column order list is the standard approach.