|
| 1 | +""" |
| 2 | +File: mapattrs.py (3.x + 2.x) |
| 3 | + |
| 4 | +Main tool: mapattrs() map all attributes on or inherited by an |
| 5 | +instance t othe instance or class from which they are inherited. |
| 6 | + |
| 7 | +Assumes dir() give all attributes of an instance. To simulate |
| 8 | +inheritance, uses eitehr the class's MRO tuple, which gives the |
| 9 | +search order for new-style classes (and all in 3.x), or a recursive |
| 10 | +traversal to infer the DFLR order of classic classes in 2.x |
| 11 | + |
| 12 | +Also here: inheritance() gives version-neutral class ordering; |
| 13 | +assorted dictionary tools using 3.x/2.7 comprehensions. |
| 14 | +""" |
| 15 | + |
| 16 | +import pprint |
| 17 | + |
| 18 | + |
| 19 | +def trace(X, label='', end='\n'): |
| 20 | + print(label + pprint.pformat(X) + end) # Print nicely |
| 21 | + |
| 22 | + |
| 23 | +def filterdictvals(D, V): |
| 24 | + """ |
| 25 | + dict D with entries for valeus V removed. |
| 26 | + filterdictvals(dict(a=1, b=2, c=1), 1) => {'b': 2} |
| 27 | + """ |
| 28 | + return {K: V2 for (K, V2) in D.items() if V2 != V} |
| 29 | + |
| 30 | + |
| 31 | +def invertdict(D): |
| 32 | + """ |
| 33 | + dict D with values changed to keys (grouped by values). |
| 34 | + Values must all be hashable to work as dict/set keys. |
| 35 | + invertdict(dict(a=1, b=2, c=1)) => {1: ['a', 'c'], 2: 'b'} |
| 36 | + """ |
| 37 | + def keysof(V): |
| 38 | + return sorted(K for K in D.keys() if D[K] == V) |
| 39 | + return {V: keysof(V) for V in set(D.values())} |
| 40 | + |
| 41 | + |
| 42 | +def dflr(cls): |
| 43 | + """ |
| 44 | + Classics depth-first left-to-right order of class tree at cls. |
| 45 | + Cycles not possible: Python disallows on __bases__ changes. |
| 46 | + """ |
| 47 | + here = [cls] |
| 48 | + for sup in cls.__bases: |
| 49 | + here += dflr(sup) |
| 50 | + return here |
| 51 | + |
| 52 | + |
| 53 | +def inheritance(instance): |
| 54 | + """ |
| 55 | + Inheritance order sequnce: new-style (MRO) or classic (DFLR) |
| 56 | + """ |
| 57 | + if (hasattr(instance.__class__, '__mro__')): |
| 58 | + return (instance,) + instance.__class__.__mro__ |
| 59 | + else: |
| 60 | + return [instance] + dflr(instance.__class__) |
| 61 | + |
| 62 | + |
| 63 | +def mapattrs(instance, withobject=False, bysource=False): |
| 64 | + """ |
| 65 | + dict with keys giving all inherited attributes of instance, |
| 66 | + with values giving the object that each is inherited from. |
| 67 | + withobject: False=remove object built-in class attributes |
| 68 | + bysource: True=group result by objects instead of attributes. |
| 69 | + Supports classes with slot that preclude __dict__ in instance. |
| 70 | + """ |
| 71 | + attr2obj = {} |
| 72 | + inherits = inheritance(instance) |
| 73 | + for attr in dir(instance): |
| 74 | + for obj in inherits: |
| 75 | + if hasattr(obj, '__dict__') and attr in obj.__dict__: |
| 76 | + attr2obj[attr] = obj |
| 77 | + break |
| 78 | + |
| 79 | + if not withobject: |
| 80 | + attr2obj = filterdictvals(attr2obj, object) |
| 81 | + |
| 82 | + return attr2obj if not bysource else invertdict(attr2obj) |
| 83 | + |
| 84 | + |
| 85 | +if __name__ == '__main__': |
| 86 | + print('Classics classes in 2.x, new-style in 3.x') |
| 87 | + class A: attr1 = 1 |
| 88 | + class B(A): attr2 = 2 |
| 89 | + class C(A): attr1 = 3 |
| 90 | + class D(B, C): pass |
| 91 | + I = D() |
| 92 | + print("Py=>%s" % I.attr1) |
| 93 | + trace(inheritance(I), 'INH\n') |
| 94 | + trace(mapattrs(I), 'ATTRS\n') |
| 95 | + trace(mapattrs(I, bysource=True), 'OBJS\n') |
| 96 | + |
| 97 | + print('New-style classes in 2.x and 3.x') |
| 98 | + class A(object): attr1 = 1 |
| 99 | + class B(A): attr2 = 2 |
| 100 | + class C(A): attr1 = 3 |
| 101 | + class D(B, C): pass |
| 102 | + I = D() |
| 103 | + print("Py=>%s" % I.attr1) |
| 104 | + trace(inheritance(I), 'INH\n') |
| 105 | + trace(mapattrs(I), 'ATTRS\n') |
| 106 | + trace(mapattrs(I, bysource=True), 'OBJS\n') |
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