156 lines
3.8 KiB
Python
156 lines
3.8 KiB
Python
"""
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Helper for looping over sequences, particular in templates.
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Often in a loop in a template it's handy to know what's next up,
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previously up, if this is the first or last item in the sequence, etc.
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These can be awkward to manage in a normal Python loop, but using the
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looper you can get a better sense of the context. Use like::
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>>> for loop, item in looper(['a', 'b', 'c']):
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... print loop.number, item
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... if not loop.last:
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... print '---'
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1 a
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---
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2 b
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---
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3 c
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"""
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import sys
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from .compat3 import basestring_
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__all__ = ['looper']
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class looper:
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"""
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Helper for looping (particularly in templates)
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Use this like::
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for loop, item in looper(seq):
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if loop.first:
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...
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"""
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def __init__(self, seq):
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self.seq = seq
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def __iter__(self):
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return looper_iter(self.seq)
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def __repr__(self):
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return '<%s for %r>' % (
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self.__class__.__name__, self.seq)
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class looper_iter:
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def __init__(self, seq):
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self.seq = list(seq)
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self.pos = 0
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def __iter__(self):
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return self
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def __next__(self):
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if self.pos >= len(self.seq):
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raise StopIteration
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result = loop_pos(self.seq, self.pos), self.seq[self.pos]
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self.pos += 1
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return result
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class loop_pos:
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def __init__(self, seq, pos):
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self.seq = seq
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self.pos = pos
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def __repr__(self):
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return '<loop pos=%r at %r>' % (
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self.seq[self.pos], self.pos)
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@property
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def index(self):
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return self.pos
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@property
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def number(self):
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return self.pos + 1
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@property
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def item(self):
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return self.seq[self.pos]
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@property
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def __next__(self):
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try:
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return self.seq[self.pos + 1]
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except IndexError:
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return None
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@property
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def previous(self):
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if self.pos == 0:
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return None
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return self.seq[self.pos - 1]
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@property
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def odd(self):
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return not self.pos % 2
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@property
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def even(self):
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return self.pos % 2
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@property
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def first(self):
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return self.pos == 0
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@property
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def last(self):
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return self.pos == len(self.seq) - 1
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@property
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def length(self):
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return len(self.seq)
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def first_group(self, getter=None):
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"""
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Returns true if this item is the start of a new group,
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where groups mean that some attribute has changed. The getter
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can be None (the item itself changes), an attribute name like
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``'.attr'``, a function, or a dict key or list index.
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"""
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if self.first:
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return True
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return self._compare_group(self.item, self.previous, getter)
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def last_group(self, getter=None):
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"""
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Returns true if this item is the end of a new group,
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where groups mean that some attribute has changed. The getter
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can be None (the item itself changes), an attribute name like
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``'.attr'``, a function, or a dict key or list index.
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"""
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if self.last:
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return True
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return self._compare_group(self.item, self.__next__, getter)
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def _compare_group(self, item, other, getter):
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if getter is None:
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return item != other
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elif (isinstance(getter, basestring_) and getter.startswith('.')):
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getter = getter[1:]
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if getter.endswith('()'):
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getter = getter[:-2]
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return getattr(item, getter)() != getattr(other, getter)()
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else:
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return getattr(item, getter) != getattr(other, getter)
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elif hasattr(getter, '__call__'):
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return getter(item) != getter(other)
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else:
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return item[getter] != other[getter]
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