On 28Apr2015 20:58, Jim Mooney Py3winXP <cybervigila...@gmail.com> wrote:
This is really puzzling me. I'm parsing a string to do some simple math
operations and practice tossing functions around. My parser works on the
first run, then it continually fails on the same input.
[...]
numbers = []
[...]
def parse_string(math_string):
"""Input: A math string with a verbal or mathematical operation
and two valid numbers to operate on. Extra numbers and operations
are ignored. Output: A tuple containing a function corresponding
to the operation and the two numbers. Returns None on failure.
"""
operation = None
tokens = math_string.split()
for token in tokens:
if token in operations:
operation = operations[token]
elif test_number(token) != None:
numbers.append(test_number(token))
if len(numbers) > 1:
break
[...]
At a first glance numbers is a global. It is reset to [] at program start, but
never again. So you're appending to it forever. I have not investigated further
as to how that affects your program's flow.
Cheers,
Cameron Simpson <c...@zip.com.au>
There are two ways of dealing with this problem: one is complicated and
messy, and the other is simple and very elegant. We don't have much time
left, so I'll just show you the complicated and messy way.
- Richard Feynman, 1981
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