CODEWITHSUNDEEP
python
Takkun
Takkun

Reputation: 8659

Quick way to find a true boolean, given several boolean variables?

Let's say you have 10 variables, one of which will be true and the others will be false. Other than having a ton of if/elif statements, is there a better way to find which variable is true and then do "something" based on which variable was true? Each "something" will be different depending on which variable is true.

Upvotes: 2

Views: 240

Answers (4)

kindall
kindall

Reputation: 184280

bools = [False, False, False, True, False]
# we're using constants here but you can use variables

# find first True value
whichbool = bools.index(True)

# now call a function based on that value
[func0, func1, func2, func3, func4][whichbool]()

If there is any possibility that there might be no True value, or more than one, you may want to check for this. The easiest way to check for both situations is to use the sum() function. True is 1 as an integer, so if you get any sum other than 1, there are too few or not enough True values in the list.

Upvotes: 4

Ned Batchelder
Ned Batchelder

Reputation: 375784

Any time you have a number of variables, and you want to pick among them based on a condition, you should consider using a dict instead.

bools['a'] = False
bools['b'] = False
bools['c'] = True

for k, v in bools.iteritems():
    if v:
        print "The true variable is", k

With the name of the variable in hand, you can invoke functions by name:

class MyHandlers(object):
    def a_is_true(self):
        # do something because of a

    def b_is_true(self):
        # do something because of b

handler = MyHandlers()
handler.getattr(k + "_is_true")()

Upvotes: 0

g.d.d.c
g.d.d.c

Reputation: 48028

Yes, there is. It'd be something like this:

def func1():
  print "function 1"

def func2():
  print "function 2"

def func3():
  print "function 3"

lookup = {'val1': func1, 'val2': func2, 'val3': func3}

toCall = 'val2'

lookup[toCall]()

This would allow you to retrieve and call a function based on the value of a variable. Not quite identical to the other answer, but extremely similar. This is a standard approach to emulating the switch statement from other languages.

Upvotes: 1

NPE
NPE

Reputation: 500703

First off, you could store the values in a list rather than in separate variables:

l = [v1, v2, v3, v4, v5, v6, v7, v8, v9, v10]
print l.index(True)

This will print 0 if v1 is true, 1 if v2 is true and so on.

This doesn't, however, solve the question of how to handle different behaviours for different variables. If you find if-elif-... objectionable, you could have a parallel list of functions to be called for each of the ten cases.

fns = [f1, f2, f3, f4, f5, f6, f7, f8, f9, f10]
fns[l.index(True)]() # call the appropriate function

Whether this can be considered an improvement over having a ton of elif blocks really depends on the amount of code associated with f1...f10.

Upvotes: 1

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