binary search in python weird behavior

binary-search, python

Solution

I'm guessing this is your bug:

low = mid + 1

Your while loop uses the variable `lo`, and you're defining a new variable called `low` within your while loop. In essence, you're never updating your `lo` variable.

Change that line to:

lo = mid + 1

and your algorithm should work.

Problem

Please look at this code: ``` def chop(array, search): lo = 0 high = len(array) - 1 while lo <= high: mid = (high + lo) /2 if array[mid] == search: return 'true' elif search > array[mid]: low = mid + 1 else: high = mid - 1 return 'false' if __name__ == '__main__': a = [1,2,3,4,5,6,7,8,9,10] print chop(a, 3) ``` I wrote this little script which is supposed to search for number in array - regular binary search. So I run the script, and for example when I put in `chop(a, 1)` I get true, when I put in `chop(a, 2)` I get true, but when I put `chop(a, 3)` I don't get an answer, just empty line in the Python Shell. Does anyone have an idea on what is going on?

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