root/galaxy-central/eggs/Paste-1.6-py2.6.egg/paste/util/looper.py

リビジョン 3, 3.9 KB (コミッタ: kohda, 14 年 前)

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