Double return in python class method

Question

When I call the following method, two returns are executed and I can't figure out why.

def Build(self, name = None):
    if self.buildData:
        try:
            installData = self.buildData.Build(name)
            return BuildResult(True, installData)
        except:
            pass
    else:
        Log("Application has no <build> data")
    return BuildResult(False, None)

What happens is this:

The method is called with a valid string, say "abc"
self.buildData.Build(name) is called and BuildResult(True, installData) constructor is run
The last return-statement is also executed

Please fix your "except:" clause to print the exception that's actually raised there. That will help you see what's happening. — S.Lott
– S.Lott, Commented Apr 7, 2011 at 12:05
What is self.buildData? Are you sure it isn't a reference back to the parent class? — Daniel Roseman
– Daniel Roseman, Commented Apr 7, 2011 at 12:07

tmg · Accepted Answer · 2011-04-07 12:23:00Z

7

Well, I guess that BuildResult() fails, exception is passed and you go into second return. You can easy test it just by adding some debug print in except - never make exceptions silent :)

edited Apr 7, 2011 at 12:23

answered Apr 7, 2011 at 12:07

tmg

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Comments

Rumple Stiltskin · Accepted Answer · 2011-04-07 12:12:33Z

1

When return BuildResult(True, installData) is executed BuildResult(True, installData) is evaluated first. My guess is, this function raises an exception which is caught and passed. After that return BuildResult(False, None) is executed.

You should see what exception is raised and handle it properly.

I would rewrite the function as follows:

def Build(self, name = None):
    if self.buildData:
        try:
            installData = self.buildData.Build(name)
        except: # TODO: catch only expected exception
            pass
        return BuildResult(True, installData)
    else:
        Log("Application has no <build> data")
    return BuildResult(False, None)

answered Apr 7, 2011 at 12:12

Rumple Stiltskin

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