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Pure Python coalesce alternative.
class Unset:
"""
This class represent an unset instance.
"""
unset = Unset()
def first_or_default(sequence, condition=unset, default=None):
"""
Returns the first or default value that matches with a condition.
"""
sequence = iter(sequence) if condition is unset else filter(condition, sequence)
try:
return next(sequence)
except StopIteration:
return default
def coalesce(*sequence, default=None):
"""
Returns the first valid element in sequence.
"""
return first_or_default(sequence, None, default=default)
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