Using timeit in an interact without string formatting

edit

As far as n is in the global namespace, the error message of your example is misleading. My example below gives the error message:

NameError: global name 'k' is not defined

def T(k):
    top = ceil(math.sqrt(k))
    print top   

@interact
def _(k=6739815371):
    timeit('T(k)')

So timeit apparently looks in the global namespace.

My first try was:

@interact
def _(k=6739815371):
    global k
    timeit('T(k)')

Traceback (most recent call last): def _(k=6739815371): File "", line 1, in <module> File "/tmp/tmpVWF0nv/___code___.py", line 8 @interact SyntaxError: name 'k' is local and global

So we have to outwit the @interact function:

@interact
def _(k0=6739815371):
    global k
    k = k0
    timeit('T(k)')

I suspect it is some python idiosyncrasy. It is somehow not getting the variable n as defined in the function declaration. The following works (for some reason using n=n again didn't work, probably because n is defined globally to be some function):

def T(n):
    top = ceil(math.sqrt(n))
    print top

@interact
def _(k=6739815371):
    T(k)
    k = k
    timeit('T(k)')