Methods for writing Parquet files using Python?

问题

I'm having trouble finding a library that allows Parquet files to be written using Python. Bonus points if I can use Snappy or a similar compression mechanism in conjunction with it.

Thus far the only method I have found is using Spark with the pyspark.sql.DataFrame Parquet support.

I have some scripts that need to write Parquet files that are not Spark jobs. Is there any approach to writing Parquet files in Python that doesn't involve pyspark.sql?

回答1:

Update (March 2017): There are currently 2 libraries capable of writing Parquet files:

fastparquet
pyarrow

Both of them are still under heavy development it seems and they come with a number of disclaimers (no support for nested data e.g.), so you will have to check whether they support everything you need.

OLD ANSWER:

As of 2.2016 there seems to be NO python-only library capable of writing Parquet files.

If you only need to read Parquet files there is python-parquet.

As a workaround you will have to rely on some other process like e.g. pyspark.sql (which uses Py4J and runs on the JVM and can thus not be used directly from your average CPython program).

回答2:

fastparquet does have write support, here is a snippet to write data to a file

from fastparquet import write
write('outfile.parq', df)

回答3:

using fastparquet you can write a pandas df to parquet either withsnappy or gzip compression as follows:

make sure you have installed the following:

$ conda install python-snappy
$ conda install fastparquet

do imports

import pandas as pd 
import snappy
import fastparquet

assume you have the following pandas df

df = pd.DataFrame(data={'col1': [1, 2], 'col2': [3, 4]})

send df to parquet with snappy compression

df.to_parquet('df.snap.parquet',compression='snappy')

send df to parquet with gzip compression

df.to_parquet('df.gzip.parquet',compression='gzip')

check:

read parquet back into pandas df

pd.read_parquet('df.snap.parquet')

pd.read_parquet('df.gzip.parquet')

output:

   col1 col2
0   1    3
1   2    4

回答4:

pyspark seems to be the best alternative right now for writing out parquet with python. It may seem like using a sword in place of needle, but thats how it is at the moment.