New submission from James Hutchison <[email protected]>:
In python is currently there a way to elegantly throw an error if a variable is
already in the current scope?
For example:
def longfunc(self, filename):
FILE = open(filename);
header = FILE.readline();
... bunch of code ...
childfiles = self.children;
for child in childfiles:
FILE = open(child);
header = FILE.readline();
... do something with header ...
for line in FILE:
... etc ...
In this case, I'm accidentally overriding the old values of FILE and header,
resulting in a bug. But I'm not going to catch this. I've had a couple of real
life bugs due to this that were a lot more subtle and lived for months without
anyone noticing the output data was slightly wrong.
This situation could be prevented if there was a way to say something along the
lines of "new FILE = open(child)" or "new header = FILE.readline()" and have
python throw an error to let me know that it already exists. This would also
make code clearer because it allows the intended scope of a variable to become
more apparent. Since "new var = something" is a syntax error, adding this
functionality wouldn't break old code, as long as python would allow for 'new'
(or whatever the keyword would end up being) to also be a variable name (like
"new new = 1" or "new = 1")
----------
components: Interpreter Core
messages: 150344
nosy: Jimbofbx
priority: normal
severity: normal
status: open
title: way to prevent accidental variable overriding
type: enhancement
versions: Python 3.2, Python 3.3, Python 3.4
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Python tracker <[email protected]>
<http://bugs.python.org/issue13678>
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