Multiplying target values with a list

Question

X = ['M','W','W','M','M','W']
NUM = [1,2,3,4,5,6]

trying to write a subroutine that will take NUM list and depending on whether the value in the corresponding list is M or W will multiply the value from Num list by either 5 when M is present and 10 with W.

have tried using two target values and index numbers with little success

Answer 1

Something like this would do what you want:

X = ['M', 'W', 'W', 'M', 'M', 'W']
NUM = [1, 2, 3, 4, 5, 6]
X_VAL = {'M': 5,
         'W': 10
         }
result = []
for index, val in enumerate(NUM):
    result.append(val * X_VAL[X[index]])

print(result)

Let me know if you need any help understanding the code.

EDIT: Like @user2357112 said you can zip both lists like this:

X = ['M', 'W', 'W', 'M', 'M', 'W']
NUM = [1, 2, 3, 4, 5, 6]
X_VAL = {'M': 5,
         'W': 10
         }
result = []
for val, x in zip(NUM, X):
    result.append(val * X_VAL[x])

print(result)

Answer 2

Using a simple list comprehension and Python's ternary operator:

X = ['M','W','W','M','M','W']
NUM = [1,2,3,4,5,6]

final = [i * (5 if j == 'M' else 10) for i, j in zip(NUM, X)]
print(final)

Output:

[5, 20, 30, 20, 25, 60]

If you had more than two letters, and a unique multiplication value for each one, you could use a dictionary:

>>> X = ['M','W','W','M','M','W', 'K', 'J', 'J', 'L']
>>> NUM = [1,2,3,4,5,6,4,2,1,8]
>>> dct = {'M': 5, 'W': 10, 'J': 8, 'K': 4, 'L': 3}
>>> [i * dct[j] for i, j in zip(NUM, X)]
[5, 20, 30, 20, 25, 60, 16, 16, 8, 24]

Answer 3

Another approach would be to use lambda functions and map :

def mult(x, num):
    factor = lambda i: 5 if i=='M' else 10
    return list(map(lambda i: factor(i[0]) * i[1],zip(x,num)))

X = ['M','W','W','M','M','W']
NUM = [1,2,3,4,5,6]

print(mult(X, NUM))

Output:

[5, 20, 30, 20, 25, 60]