Python方法可以检查它是否已经从内部调用吗？

Question

假设我有一个Python函数f和fhelp。fhelp旨在以递归方式调用自身。f不应递归调用。有没有办法f确定是否已递归调用它？

Answer 1

为此使用追溯模块：

>>> import traceback
>>> def f(depth=0):
...     print depth, traceback.print_stack()
...     if depth < 2:
...         f(depth + 1)
...
>>> f()
0  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in f
 None
1  File "<stdin>", line 1, in <module>
  File "<stdin>", line 4, in f
  File "<stdin>", line 2, in f
 None
2  File "<stdin>", line 1, in <module>
  File "<stdin>", line 4, in f
  File "<stdin>", line 4, in f
  File "<stdin>", line 2, in f
 None

因此，如果堆栈中的任何条目指示从f调用了代码，则该调用是（间接）递归的。该traceback.extract_stack方法使您可以轻松访问此数据。if len(l[2] ...下面的示例中的语句仅计算函数名称的完全匹配数。为了使它更漂亮（感谢agf的想法），您可以将其变成装饰器：

>>> def norecurse(f):
...     def func(*args, **kwargs):
...         if len([l[2] for l in traceback.extract_stack() if l[2] == f.func_name]) > 0:
...             raise Exception, 'Recursed'
...         return f(*args, **kwargs)
...     return func
...
>>> @norecurse
... def foo(depth=0):
...     print depth
...     foo(depth + 1)
...
>>> foo()
0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in func
  File "<stdin>", line 4, in foo
  File "<stdin>", line 5, in func
Exception: Recursed