Python variable between if and elif

Question

The following is invalid syntax as the elif needs to be right after the if block:

def get_number(self, bsObj):
    temp = self.get_data('text1', bsObj)
    if temp > -1:
        return temp
    temp = self.get_info('text', bsObj)
    elif temp > -1:
        return temp
    else:
        return 0

I only want to return the result of self.get_info('text', bsObj) if self.get_data('text1', bsObj) is less than -1.

I could fix it by doing this, but it seems very ineffective to call the same function twice:

def get_number(self, bsObj):
    if self.get_data('text1', bsObj) > -1:
        return self.get_data('text1', bsObj)
    elif self.get_info('text', bsObj) > -1:
        return self.get_data('text', bsObj)
    else:
        return 0

Thanks to everyone who answered below. I now know that I missed something very important about what the return statement does. I mistakenly thought that if both if statementa were True the first return statement would be replaced by the second. I feel really dumb now, but I'm also very happy that I now learned this very important point. It will really make coding much simpler for me now. So thank you to all of you. — Wessi
– Wessi, Commented Jul 14, 2017 at 17:46

willeM_ Van Onsem · Accepted Answer · 2017-07-14 17:36:10Z

5

You can use a second if:

def get_number(self, bsObj):
    temp = self.get_data('text1', bsObj)
    if temp > -1:
        return temp
    temp = self.get_info('text', bsObj)
    if temp > -1:
        return temp
    else:
        return 0

Since the first if contains a return statement, the interpreter will never reach your elif line if the constraint is satisfied.

answered Jul 14, 2017 at 17:36

willeM_ Van Onsem

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Comments

Alex Hall · Accepted Answer · 2017-07-14 17:35:38Z

4

Just use if instead of elif. The el[se] is redundant because of the return anyway.

answered Jul 14, 2017 at 17:35

Alex Hall

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Comments

Prune · Accepted Answer · 2017-07-14 17:39:22Z

2

Note that the return exits the function, so you don't have to worry about your branch logic. You're correct that you shouldn't call a function twice: continue to use temp for each call.

You have two choices. The first is to simply use a new if; the old one already left the function.

temp = self.get_data('text1', bsObj)
if temp > -1:
    return temp

temp = self.get_info('text', bsObj)
if temp > -1:
    return temp

return 0

The other choice is to correctly wrap the "else" logic in that block:

temp = self.get_data('text1', bsObj)
if temp > -1:
    return temp
else:
    temp = self.get_info('text', bsObj)
    if temp > -1:
        return temp
    else:
        return 0

answered Jul 14, 2017 at 17:39

Prune

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Comments

jmoon · Accepted Answer · 2017-07-14 17:42:01Z

1

Try this:

def get_number(self, bsObj):
    temp = self.get_data('text1', bsObj)
    if temp < -1:
        temp = self.get_info('text', bsObj)
    elif temp = -1:
        return 0
    else:
        pass
    return temp

So what I've done is switched your if and elif cases. You only want to change your temp definition if temp < -1, and if temp = -1. (really, even the pass is a little redundant, if you don't want to keep it you should be able to get rid of it just fine.)

answered Jul 14, 2017 at 17:42

jmoon

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Comments

Uri Goren · Accepted Answer · 2017-07-14 17:49:28Z

1

Written in a more concise way:

def get_number(self, bsObj):
    temp = self.get_data('text1', bsObj) if self.get_data('text1', bsObj)>-1 else self.get_info('text', bsObj)
    return temp if temp>-1 else 0

answered Jul 14, 2017 at 17:49

Uri Goren

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Comments

NinjaKitty · Accepted Answer · 2017-07-14 17:51:10Z

1

I don't know if this works, but I decided to post this for fun.

def get_number(self, bsObj):
    temp = self.get_data('text1', bsObj)
    temp2 = self.get_info('text', bsObj)
    return temp if temp > -1 else temp2 if temp2 > -1 else 0

answered Jul 14, 2017 at 17:51

NinjaKitty

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2 Comments

Uri Goren Over a year ago

Note that get_info is being called, regardless of the value of self.get_data('text1', bsObj), where in the original code, it does not

NinjaKitty Over a year ago

Yes I am aware of that. Efficiency though is relative to whether or not self.get_info() will be called often or not every time get_number() is called. We do not know the answer to that.

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