python - replace the boolean value of a list with the values from two different lists [duplicate]

Question

I have one list with boolean values like

lyst = [True,True,False,True,False]

and two different lists for example like:

car = ['BMW','VW','Volvo']
a = ['b','c']

I just want to replace True with the values from car and False with the values from a. or make a new list with the sequence from lyst and values from car and a. The result should be

[BMW,VW,b,Volvo,c].

my code so far:

for elem1,elem2,elem3 in zip(lyst,car,a):
    subelem2=elem2
    subelem3=elem3
    if elem1 != True:
        result_list.append(subelem2)
    else: 
        result_list.append(subelem3)

but this creates a list match longer than 5.

How can i do this?

Answer 1

car = iter(car)
a = iter(a)
[next(car) if item else next(a) for item in lyst]

---

Ok, I couldn't help myself:

car = iter(car)
a = iter(a)
[(flag and next(car)) or next(a) for flag in lyst]

This makes use of some boolean expression features:

• a boolean and expression will NOT evaluate the second operand if the first operand is False
• a boolean and expression will return the second operand (the actual object) if both operands evaluate to True
• a boolean or expression will return the first object that evaluates to True

A potential problem would be if any items in car or a evaluate to False. Also this isn't as readable as the ternary in the first solution.

But it was fun.

---

I guess I'll add that after looking at this again, I probably shouldn't have reassigned the original list names - I should have chosen something different for the iterator names. Once exhausted, the iterators cannot be reset and since the list names were reassigned, the original list information is lost.