Backend File-systems

Fastparquet can use alternatives to the local disk for reading and writing parquet.

One example of such a backend file-system is s3fs, to connect to AWS’s S3 storage. In the following, the login credentials are automatically inferred from the system (could be environment variables, or one of several possible configuration files).

import s3fs
from fastparquet import ParquetFile
s3 = s3fs.S3FileSystem()
myopen =
pf = ParquetFile('/mybucket/data.parquet', open_with=myopen)
df = pf.to_pandas()

The function myopen provided to the constructor must be callable with f(path, mode) and produce an open file context.

The resultant pf object is the same as would be generated locally, and only requires a relatively short read from the remote store. If ‘/mybucket/data.parquet’ contains a sub-key called “_metadata”, it will be read in preference, and the data-set is assumed to be multi-file.

Similarly, providing an open function and another to make any necessary directories (only necessary in multi-file mode), we can write to the s3 file-system:

write('/mybucket/output_parq', data, file_scheme='hive',
      row_group_offsets=[0, 500], open_with=myopen, mkdirs=noop)

(In the case of s3, no intermediate directories need to be created)