Unpack one list to another replacing a special symbol in Python-CodePudding

I have two lists:

a = ['first', '___' , 'third', '___' ]
b = ['second', 'fourth']

I want to unpack b into a to replace the special character ___ while keeping the current order. The result should be

res = ['first', 'second' , 'third', 'fourth']

What is the most efficient way to do that?

CodePudding user response：

One approach is to use next:

a = ['first', '___', 'third', '___']
b = ['second', 'fourth']

iter_b = iter(b)
res = [next(iter_b) if ei == '___' else ei for ei in a]
print(res)

Output

['first', 'second', 'third', 'fourth']