Mercurial > hg > Lemuriformes
diff lemuriformes/cast.py @ 5:dbbf5344868c
add utlities for casting data
author | Jeff Hammel <k0scist@gmail.com> |
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date | Sun, 10 Dec 2017 11:51:39 -0800 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/lemuriformes/cast.py Sun Dec 10 11:51:39 2017 -0800 @@ -0,0 +1,105 @@ +""" +methods for casting data +""" + +import datetime +from collections import OrderedDict + + +try: + # python2 + string = (str, unicode) +except NameError: + # python3 + string = (str,) + +def isstring(f): + return isinstance(f, string) + +# types we expect to encounter +types = OrderedDict([('int', int), + ('float', float), + ('str', str)]) + + +def keyvalue(_string, separator='='): + """ + cast `_string` to [`key`, `value`] split on `separator` + """ + + if separator not in _string: + raise AssertionError("Separator '{}' not in '{}'".format(separator, + _string)) + return _string.split(separator, 1) + + +def string_to_bool(string): + """cast a string to a `bool`""" + return {'true': True, + 'false': False}.get(string.lower()) + + +def unify(item, codec='utf-8'): + """cast item to unicode carefully if a string; otherwise, return it""" + + if not isinstance(item, string): + return item + return item.encode(codec, 'ignore') + + +def datetime_handler(x): + """handler for JSON serialization""" + + # Ref + # https://stackoverflow.com/questions/35869985/datetime-datetime-is-not-json-serializable + if isinstance(x, datetime.datetime): + return x.isoformat() + + # go through the normal types for type casting + # (and hope nothing "weird" happens") + for _type in types.values(): + try: + return str(_type(x)) + except ValueError: + continue + + # worst case scenario + raise TypeError("Unknown type: {x}".format(x=x)) + + +def isiterable(obj): + """determines if `obj` is iterable""" + + try: + iter(obj) + return True + except TypeError: + return False + + +def iterable(obj): + """make an iterable out of `obj`""" + return obj if isiterable(obj) else (obj,) + + +def infer(strings, types=types.values()): + """ + inferrred the type of a bunch of strings + """ + for _type in types: + for s in strings: + try: + _type(s) + except ValueError: + break + else: + return _type + + +def cast(strings, types=types.values()): + """ + cast `strings` to `types` based on inference + """ + + _type = infer(strings, types=types) + return [_type(s) for s in strings]