Concatenate pandas DataFrame to Existing CSV File in Python (Example Code)

In this tutorial, I’ll explain how to append a new pandas DataFrame to an existing CSV file in Python.

Setting up the Example

import pandas as pd                             # Import pandas library
my_df = pd.DataFrame({'A':range(0, 5),          # Construct pandas DataFrame in Python
                      'B':['x', 'y', 'x', 'x', 'y'],
                      'C':range(15, 10, - 1)})
print(my_df)
#    A  B   C
# 0  0  x  15
# 1  1  y  14
# 2  2  x  13
# 3  3  x  12
# 4  4  y  11
my_df.to_csv('my_df.csv', index = False)        # Saving pandas DataFrame as CSV

Example: Add New pandas DataFrame to Existing CSV File Vertically

my_df_new = pd.DataFrame({'A':range(10, 13),    # Construct another DataFrame
                          'B':['foo', 'bar', 'foo'],
                          'C':range(100, 103)})
print(my_df_new)
#     A    B    C
# 0  10  foo  100
# 1  11  bar  101
# 2  12  foo  102
my_df_new.to_csv('my_df.csv',                   # Append data at the bottom
                 mode = 'a',
                 header = False,
                 index = False)

Further Resources & Related Articles

In addition, you may want to have a look at the related tutorials on this website:

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