My question is on control flows with if-statements and arrays, basically, I am extracting some information to an array x (given conditions a,b) and the flow gets executed depending on whether there is some information extracted or there was no information. My code looks like that:

if a:
   x = ...
   if not x:
      if b: #repeated
         x = ...
         if not x:
            raise Exception
elif b: #repeated
         x = ...
         if not x:
            raise Exception

Is there any elegant way to skip to elif condition automatically after 'if not x'? My primary focus is on a, if a is not present or doesn't contain any information, I am checking existence of b and whether it's empty. If b empty I am raising an exception (here i might actually proceed to else: raise Exception however it's the same thing as above and I don't know how to control such a flow i.e. redirect to another statement).

I've tried 'break' however it doesn't work for statements not nested in the for/while loops.

Thanks in advance!

Some clarification based on comments:

1. x gets assigned to an xmltree element and the element is different for a and b,
2. The 'if a' is about checking if item1 is present in an array, then I am checking if the element in xml tree assigned to it contains some information, if not I fall back on the default option b, and also checking if item2 now exists and if it contains information; if none of the abovementioned cases - the program should exit at this point

CodePudding user response：

Assuming the assignment to x is the same (or at least varies only in the value a or b used, you can use a loop with an else clause:

for thing in [a,b]:
    if not thing:
        continue
    x = ...  # can depend on thing
    if x:
        break
else:
    raise Exception

The else clause is only executed if the loop terminates due to exhaustion of the iterable, not if a break statement is executed.

CodePudding user response：

Since there is limited context I can only imagine what you want. If you use python 3.10, you might be able to use the match statement for your use case. Here's what I imagine this could look like but we can refurbish this further in the comments:

class XMLNode:

    def __init__(self, subnode, label):
        self.subnode = subnode
        self.label = label

node = ...

match node
    case XMLNode(subnode=a, label=_):
        pass
    case XMLNode(subnode=b, label=_):
        pass