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5
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1 """
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2 methods for casting data
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3 """
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4
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5 import datetime
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6 from collections import OrderedDict
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7
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8
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9 try:
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10 # python2
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11 string = (str, unicode)
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12 except NameError:
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13 # python3
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14 string = (str,)
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15
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16 def isstring(f):
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17 return isinstance(f, string)
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18
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19 # types we expect to encounter
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20 types = OrderedDict([('int', int),
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21 ('float', float),
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22 ('str', str)])
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23
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24
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25 def keyvalue(_string, separator='='):
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26 """
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27 cast `_string` to [`key`, `value`] split on `separator`
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28 """
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29
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30 if separator not in _string:
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31 raise AssertionError("Separator '{}' not in '{}'".format(separator,
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32 _string))
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33 return _string.split(separator, 1)
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34
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35
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36 def string_to_bool(string):
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37 """cast a string to a `bool`"""
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38 return {'true': True,
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39 'false': False}.get(string.lower())
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40
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41
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42 def unify(item, codec='utf-8'):
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43 """cast item to unicode carefully if a string; otherwise, return it"""
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44
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45 if not isinstance(item, string):
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46 return item
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47 return item.encode(codec, 'ignore')
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48
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49
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50 def datetime_handler(x):
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51 """handler for JSON serialization"""
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52
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53 # Ref
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54 # https://stackoverflow.com/questions/35869985/datetime-datetime-is-not-json-serializable
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55 if isinstance(x, datetime.datetime):
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56 return x.isoformat()
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57
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58 # go through the normal types for type casting
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59 # (and hope nothing "weird" happens")
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60 for _type in types.values():
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61 try:
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62 return str(_type(x))
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63 except ValueError:
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64 continue
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65
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66 # worst case scenario
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67 raise TypeError("Unknown type: {x}".format(x=x))
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68
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69
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70 def isiterable(obj):
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71 """determines if `obj` is iterable"""
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72
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73 try:
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74 iter(obj)
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75 return True
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76 except TypeError:
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77 return False
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78
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79
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80 def iterable(obj):
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81 """make an iterable out of `obj`"""
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82 return obj if isiterable(obj) else (obj,)
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83
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84
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85 def infer(strings, types=types.values()):
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86 """
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87 inferrred the type of a bunch of strings
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88 """
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89 for _type in types:
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90 for s in strings:
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91 try:
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92 _type(s)
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93 except ValueError:
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94 break
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95 else:
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96 return _type
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97
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98
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99 def cast(strings, types=types.values()):
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100 """
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101 cast `strings` to `types` based on inference
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102 """
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103
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104 _type = infer(strings, types=types)
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105 return [_type(s) for s in strings]
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