test.py

import magic
import sys
from pprint import pprint


f = sys.argv[1]


def _is_ascii(f, mime):
    if mime == 'ASCII text':
        return True


def _is_rss(f, mime):
    if not _is_xml(f, mime):
        return


def _is_xml(f, mime):
    if mime == 'XML document text':
        return 'xml'


def _is_json(f, mime):
    if not _is_ascii(f, mime):
        return

    first = f.readline().rstrip("\n")
    last = first
    try:
        last = f.readlines()[-1].rstrip("\n")
    except Exception:
        pass

    if not (first.startswith("'[{") or first.startswith("'{")):
        return

    if not (last.endswith("}]'") or last.endswith("}'")):
        return

    return 'json'


def _is_delimited(f, mime):
    if not _is_ascii(f, mime):
        return

    m = {
        "\t": 'tsv',
        ',': 'csv',
        '|': 'pipe',
        ';': 'semicolon'
    }

    first = f.readline().rstrip("\n")
    while first.startswith('#'):
        first = f.readline().rstrip("\n")

    second = f.readline().rstrip("\n")
    for d in m:
        c = first.count(d)
        if c == 0:
            continue

        if second.count(d) == c:
            return m[d]

    return False

TESTS = [
    _is_delimited,
    _is_json,
    _is_xml,
]


def feed_type(f, mime):
    t = None
    for tt in TESTS:
        t = tt(f, mime)
        if t:
            return t

with open(f) as FILE:
    mime_type = magic.from_file(f)
    print(mime_type)

    print(feed_type(FILE, mime_type))