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# Base classes for readers and writers.
# Author: David Alexander
from __future__ import absolute_import
import gzip
from os.path import abspath, expanduser
__all__ = [ "ReaderBase", "WriterBase" ]
def isFileLikeObject(o):
return hasattr(o, "read") and hasattr(o, "write")
def getFileHandle(filenameOrFile, mode="r"):
"""
Given a filename not ending in ".gz", open the file with the
appropriate mode.
Given a filename ending in ".gz", return a filehandle to the
unzipped stream.
Given a file object, return it unless the mode is incorrect--in
that case, raise an exception.
"""
assert mode in ("r", "w")
if isinstance(filenameOrFile, basestring):
filename = abspath(expanduser(filenameOrFile))
if filename.endswith(".gz"):
return gzip.open(filename, mode)
else:
return open(filename, mode)
elif isFileLikeObject(filenameOrFile):
return filenameOrFile
else:
raise Exception("Invalid type to getFileHandle")
class ReaderBase(object):
def __init__(self, f):
"""
Prepare for iteration through the records in the file
"""
self.file = getFileHandle(f, "r")
if hasattr(self.file, "name"):
self.filename = self.file.name
else:
self.filename = "(anonymous)"
def close(self):
"""
Close the underlying file
"""
self.file.close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
self.close()
def __repr__(self):
return "<%s for %s>" % (type(self).__name__, self.filename)
class WriterBase(object):
def __init__(self, f):
"""
Prepare for output to the file
"""
self.file = getFileHandle(f, "w")
if hasattr(self.file, "name"):
self.filename = self.file.name
else:
self.filename = "(anonymous)"
def close(self):
"""
Close the underlying file
"""
self.file.close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
self.close()
def __repr__(self):
return "<%s for %s>" % (type(self).__name__, self.filename)
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