high=None advantage over high=len(a) in bisect.bisect_left

Question

I am learning 8.6. bisect — Array bisection algorithm,

bisect.bisect_left(a, x, lo=0, hi=len(a)) has default values of lo=0, hi=len(a),
When I checked the source code and found that hi=len(a) is not set as default directly,

def bisect_right(a, x, lo=0, hi=None):
    if lo < 0:
        raise ValueError('lo must be non-negative')
    if hi is None:
        hi = len(a)
    while lo < hi:
        mid = (lo+hi)//2  
        if x < a[mid]:
            hi = mid
        else:
            lo = mid+1
    return lo

It's achieved by a if check None.

What's the benefit do extra checking than set it as default straightly?

Because `a` hasn't been defined yet. The parameter doesn't exist until inside the function definition; other parameters can't see it. — chrisaycock, Aug 21 '18 at 02:34
How smart... Could you please transmit the comment to answer as a forwards reference. @chrisaycock — AbstProcDo, Aug 21 '18 at 02:42
The other question does not attempt to apply `len` to the parameter, but the accepted answer fully covers your situation. — Mad Physicist, Aug 21 '18 at 02:51

score 2 · Accepted Answer · answered Aug 21 '18 at 02:44

2

Because a hasn't been defined yet. The parameter doesn't exist until inside the function definition; other parameters can't see it.

answered Aug 21 '18 at 02:44

chrisaycock

36,470
14
88
125

high=None advantage over high=len(a) in bisect.bisect_left

1 Answers1