How to concatenate multiple pandas.DataFrames without running into MemoryError

Question

I have three DataFrames that I\'m trying to concatenate.

concat_df = pd.concat([df1, df2, df3])

This results in a MemoryError. How can I re

Answer 1

I advice you to put your dataframes into single csv file by concatenation. Then to read your csv file.

Execute that:

# write df1 content in file.csv
df1.to_csv('file.csv', index=False)
# append df2 content to file.csv
df2.to_csv('file.csv', mode='a', columns=False, index=False)
# append df3 content to file.csv
df3.to_csv('file.csv', mode='a', columns=False, index=False)

# free memory
del df1, df2, df3

# read all df1, df2, df3 contents
df = pd.read_csv('file.csv')

If this solution isn't enougth performante, to concat larger files than usually. Do:

df1.to_csv('file.csv', index=False)
df2.to_csv('file1.csv', index=False)
df3.to_csv('file2.csv', index=False)

del df1, df2, df3

Then run bash command:

cat file1.csv >> file.csv
cat file2.csv >> file.csv
cat file3.csv >> file.csv

Or concat csv files in python :

def concat(file1, file2):
    with open(file2, 'r') as filename2:
        data = file2.read()
    with open(file1, 'a') as filename1:
        file.write(data)

concat('file.csv', 'file1.csv')
concat('file.csv', 'file2.csv')
concat('file.csv', 'file3.csv')

After read:

df = pd.read_csv('file.csv')