[英]how to I get the total number of stack frames used in recursion in Python?
这是计算斐波那契数列的简单代码:
def fib(n):
if n==0 or n==1:
return 1
else:
return fib(n-1)+fib(n-2)
如果n = 10,我想知道此计算涉及多少堆栈帧。 有没有一种实时获取方法?
最简单的解决方案是添加一个额外的参数,然后将其穿过结果:
def fib(n, depth=1):
if n == 0 or n == 1:
return (1, depth)
else:
result1, depth1 = fib(n-1, depth+1)
result2, depth2 = fib(n-2, depth+1)
return (result1 + result2, max(depth1, depth2))
这将返回斐波那契数和递归深度。
测试:
>>> list(map(fib, range(5)))
[(1, 1), (1, 1), (2, 2), (3, 3), (5, 4)]
import inspect
def fib(n):
fib.calls += 1
print "depth =", len(inspect.stack())
print "calls =", fib.calls
if n == 0 or n == 1:
return 1
else:
return fib(n - 1) + fib(n - 2)
例如
>>> fib.calls = 0
>>> fib(5)
depth = 2
calls = 1
depth = 3
calls = 2
depth = 4
calls = 3
depth = 5
calls = 4
depth = 6
calls = 5
depth = 6
calls = 6
depth = 5
calls = 7
depth = 4
calls = 8
depth = 5
calls = 9
depth = 5
calls = 10
depth = 3
calls = 11
depth = 4
calls = 12
depth = 5
calls = 13
depth = 5
calls = 14
depth = 4
calls = 15
8
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