|
| 1 | +""" |
| 2 | +Helper for looping over sequences, particular in templates. |
| 3 | +
|
| 4 | +Often in a loop in a template it's handy to know what's next up, |
| 5 | +previously up, if this is the first or last item in the sequence, etc. |
| 6 | +These can be awkward to manage in a normal Python loop, but using the |
| 7 | +looper you can get a better sense of the context. Use like:: |
| 8 | +
|
| 9 | + >>> for loop, item in looper(['a', 'b', 'c']): |
| 10 | + ... print loop.number, item |
| 11 | + ... if not loop.last: |
| 12 | + ... print '---' |
| 13 | + 1 a |
| 14 | + --- |
| 15 | + 2 b |
| 16 | + --- |
| 17 | + 3 c |
| 18 | +
|
| 19 | +""" |
| 20 | + |
| 21 | +basestring_ = (bytes, str) |
| 22 | + |
| 23 | +__all__ = ['looper'] |
| 24 | + |
| 25 | + |
| 26 | +class looper: |
| 27 | + """ |
| 28 | + Helper for looping (particularly in templates) |
| 29 | +
|
| 30 | + Use this like:: |
| 31 | +
|
| 32 | + for loop, item in looper(seq): |
| 33 | + if loop.first: |
| 34 | + ... |
| 35 | + """ |
| 36 | + |
| 37 | + def __init__(self, seq): |
| 38 | + self.seq = seq |
| 39 | + |
| 40 | + def __iter__(self): |
| 41 | + return looper_iter(self.seq) |
| 42 | + |
| 43 | + def __repr__(self): |
| 44 | + return '<%s for %r>' % ( |
| 45 | + self.__class__.__name__, self.seq) |
| 46 | + |
| 47 | + |
| 48 | +class looper_iter: |
| 49 | + |
| 50 | + def __init__(self, seq): |
| 51 | + self.seq = list(seq) |
| 52 | + self.pos = 0 |
| 53 | + |
| 54 | + def __iter__(self): |
| 55 | + return self |
| 56 | + |
| 57 | + def __next__(self): |
| 58 | + if self.pos >= len(self.seq): |
| 59 | + raise StopIteration |
| 60 | + result = loop_pos(self.seq, self.pos), self.seq[self.pos] |
| 61 | + self.pos += 1 |
| 62 | + return result |
| 63 | + |
| 64 | + |
| 65 | +class loop_pos: |
| 66 | + |
| 67 | + def __init__(self, seq, pos): |
| 68 | + self.seq = seq |
| 69 | + self.pos = pos |
| 70 | + |
| 71 | + def __repr__(self): |
| 72 | + return '<loop pos=%r at %r>' % ( |
| 73 | + self.seq[self.pos], self.pos) |
| 74 | + |
| 75 | + def index(self): |
| 76 | + return self.pos |
| 77 | + index = property(index) |
| 78 | + |
| 79 | + def number(self): |
| 80 | + return self.pos + 1 |
| 81 | + number = property(number) |
| 82 | + |
| 83 | + def item(self): |
| 84 | + return self.seq[self.pos] |
| 85 | + item = property(item) |
| 86 | + |
| 87 | + def __next__(self): |
| 88 | + try: |
| 89 | + return self.seq[self.pos + 1] |
| 90 | + except IndexError: |
| 91 | + return None |
| 92 | + __next__ = property(__next__) |
| 93 | + |
| 94 | + def previous(self): |
| 95 | + if self.pos == 0: |
| 96 | + return None |
| 97 | + return self.seq[self.pos - 1] |
| 98 | + previous = property(previous) |
| 99 | + |
| 100 | + def odd(self): |
| 101 | + return not self.pos % 2 |
| 102 | + odd = property(odd) |
| 103 | + |
| 104 | + def even(self): |
| 105 | + return self.pos % 2 |
| 106 | + even = property(even) |
| 107 | + |
| 108 | + def first(self): |
| 109 | + return self.pos == 0 |
| 110 | + first = property(first) |
| 111 | + |
| 112 | + def last(self): |
| 113 | + return self.pos == len(self.seq) - 1 |
| 114 | + last = property(last) |
| 115 | + |
| 116 | + def length(self): |
| 117 | + return len(self.seq) |
| 118 | + length = property(length) |
| 119 | + |
| 120 | + def first_group(self, getter=None): |
| 121 | + """ |
| 122 | + Returns true if this item is the start of a new group, |
| 123 | + where groups mean that some attribute has changed. The getter |
| 124 | + can be None (the item itself changes), an attribute name like |
| 125 | + ``'.attr'``, a function, or a dict key or list index. |
| 126 | + """ |
| 127 | + if self.first: |
| 128 | + return True |
| 129 | + return self._compare_group(self.item, self.previous, getter) |
| 130 | + |
| 131 | + def last_group(self, getter=None): |
| 132 | + """ |
| 133 | + Returns true if this item is the end of a new group, |
| 134 | + where groups mean that some attribute has changed. The getter |
| 135 | + can be None (the item itself changes), an attribute name like |
| 136 | + ``'.attr'``, a function, or a dict key or list index. |
| 137 | + """ |
| 138 | + if self.last: |
| 139 | + return True |
| 140 | + return self._compare_group(self.item, self.__next__, getter) |
| 141 | + |
| 142 | + def _compare_group(self, item, other, getter): |
| 143 | + if getter is None: |
| 144 | + return item != other |
| 145 | + elif (isinstance(getter, basestring_) |
| 146 | + and getter.startswith('.')): |
| 147 | + getter = getter[1:] |
| 148 | + if getter.endswith('()'): |
| 149 | + getter = getter[:-2] |
| 150 | + return getattr(item, getter)() != getattr(other, getter)() |
| 151 | + else: |
| 152 | + return getattr(item, getter) != getattr(other, getter) |
| 153 | + elif hasattr(getter, '__call__'): |
| 154 | + return getter(item) != getter(other) |
| 155 | + else: |
| 156 | + return item[getter] != other[getter] |
0 commit comments