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aaronmk
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# Useful functions and classes
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import collections
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931
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#### Function wrappers for statements
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def noop(*args, **kw_args): pass
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def and_(a, b): return a and b
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791
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aaronmk
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#### Object metadata
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341
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def type_name(value): return type(value).__name__
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135
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def module(value): return type(value).__module__.split('.')
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def root_module(value): return module(value)[0]
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1007
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aaronmk
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#### Type checking
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791
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class ConstraintError(ValueError):
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def __init__(self, check_func, value):
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795
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ValueError.__init__(self, str(value)+' must satisfy constraint '
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+check_func.__name__)
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791
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836
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def cast(type_, val):
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1046
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'''Passes None through. Does not cast a subclass to a superclass (which
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doesn't make sense in a dynamically-typed language).'''
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if val != None and not isinstance(val, type_): val = type_(val)
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836
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return val
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791
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def is_str(val): return isinstance(val, basestring)
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1007
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aaronmk
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def is_list(val): return isinstance(val, list)
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1046
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aaronmk
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#### Basic types
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def none_if(val, none_val):
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if cast(type(none_val), val) == none_val: return None
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else: return val
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791
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#### Iterables
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135
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def first(iter_): return iter_.next()
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133
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def skip(iter_, func):
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# Advance iter while func is True
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try:
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while func(iter_.curr()): iter_.next()
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except StopIteration: pass # nothing after the matching elements
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934
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def list_subset(list_, idxs):
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subset = []
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for idx in idxs:
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try: subset.append(list_[idx])
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except IndexError: pass
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return subset
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791
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aaronmk
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class CheckedIter:
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def __init__(self, check_func, iterable):
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self.check_func = check_func
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self.iter_ = iterable.__iter__()
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def __iter__(self): return self
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def next(self):
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entry = self.iter_.next()
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if self.check_func(entry): return entry
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else: raise ConstraintError(self.check_func, entry)
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1008
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aaronmk
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#### Lists
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def list_get(list_, idx, default=None):
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try: return list_[idx]
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except IndexError: return default
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1012
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aaronmk
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def list_eq_is(list0, list1):
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'''Compares two lists using is'''
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if len(list0) != len(list1): return False
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for i in xrange(len(list0)):
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if list0[i] is not list1[i]: return False
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return True
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791
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aaronmk
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#### Dicts
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330
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aaronmk
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def rename_key(dict_, orig, new): dict_[new] = dict_.pop(orig)
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466
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aaronmk
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467
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aaronmk
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def dict_subset(dict_, keys):
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subset = dict()
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for key in keys:
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try: subset[key] = dict_[key]
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except KeyError: pass
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return subset
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1068
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aaronmk
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class DefaultDict(collections.defaultdict):
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def __init__(self, dict_, default=None):
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collections.defaultdict.__init__(self, lambda: default, dict_)
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def dict_subset_right_join(dict_, keys):
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'''Gets a subset of a dict, using None for subset keys that don't exist'''
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return dict_subset(DefaultDict(dict_), keys)
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