Help for simplifying code

[perfringo]

Let's explain what different parts are doing and then put them all together:


bool(condition) evaluates whether condition is True or False:

>>> condition = ''      # empty string (list, tuple, dict etc) is False                                   
>>> bool(condition)                                       
False
>>> condition = 42                                        
>>> bool(condition)                                       
True

In Python True and False are 1 and 0:

>>> False == 0                                            
True
>>> True == 1                                             
True

So 'bool(condition)' evaluates and returns False (0) or True (1). This result is used as index:

>>> condition = 42
>>> ['first', 'second'][bool(condition)]                 
'second'                                      # True is 1 and therefore item at index 1 is returned
>>> condition = ''                                        
['first', 'second'][bool(condition)]          # False is 0 and item at index 0 is returned                
'first'

Alternatively it can be expressed this way:

>>> x = 7 < 42                                            
>>> ['first', 'second'][x]                                
'second'
>>> x = 7 > 42                                            
>>> ['first', 'second'][x]                                
'first'

This enables to return either first or second item in list depending whether condition is true or false.

As it was required to have values 10..12 or None depending on condition truthiness list comprehension is used to emit required values, evaluate condition and return corresponding item: 'give me number or None based on whether condition is true or not for every number in range 10..12'

>>> condition = ''                                        
>>> [[number, None][bool(condition] for number in range(10, 13)]                         
>>> [10, 11, 12]

Returned list is unpacked into variables:

>>> first, second, third = [[number, None][bool(condition)] for number in range(10, 13)]                         
>>> first                                                 
10
>>> second                                                
11
>>> third
12