Source code for epygram.formats_factory

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
Utilities to play with resource formats:

- guess the format of an existing resource in a given container,
- create a Resource instance with a generic function,
  eventually (if already existing) without knowing its format *a priori*.
- ... 
"""

from footprints import proxy as fpx

from epygram import config, epygramError



def guess(filename):
    """
    Returns the name of the format of the resource located at a given 
    **filename**, if succeeded.
    """
    
    for f in config.implemented_formats: # and not the list of dataformat from footprints collectors, because the order is important.
        try:
            r = fpx.dataformat(filename=filename, openmode='r', format=f)
            r.close()
            fmt = f
            break
        except Exception:
            fmt = 'unknown'
    
    return fmt

def resource(filename, openmode, fmt=None, **kwargs):
    """
    Returns an instance of Resource of the requested *fmt* format,
    located at the given *filename* (:class:`epygram.base.File`, ...),
    and with the given *openmode*.
    
    If *fmt* is not given, tries to guess it (only for *openmode* 'r' or 'a').
    
    Other *kwargs* are passed to the resource constructor.
    """
    
    if fmt == None and openmode in ('r', 'a'):
        fmt = guess(filename)
        if fmt == 'unknown':
            raise epygramError("unable to guess format of resource at: "+filename)
    elif fmt == None and openmode == 'w':
        raise epygramError("must specify 'fmt' argument with 'openmode' == 'w'.")
    
    return fpx.dataformat(filename=filename, openmode=openmode, format=fmt, **kwargs)