Course 3 - Data Collection and Processing with Python - Week 2 - 23.5 Zip

23_5_Zip.py

# The zip function takes multiple lists and turns them into a list of tuples 
# (actually, an iterator, but they work like lists for most practical purposes), 
# pairing up all the first items as one tuple, all the second items as a tuple, and so on. 
# Then we can iterate through those tuples, and perform some operation on all the first items, 
# all the second items, and so on.

L1 = [3, 4, 5]
L2 = [1, 2, 3]
L4 = list(zip(L1, L2))
print(L4)

# Output: [(3, 1), (4, 2), (5, 3)]



# Here’s what happens when you loop through the tuples.

L1 = [3, 4, 5]
L2 = [1, 2, 3]
L3 = []
L4 = list(zip(L1, L2))

for (x1, x2) in L4:
    L3.append(x1+x2)

print(L3)

# Output: [4, 6, 8]


# Or, simplifying and using a list comprehension:

L1 = [3, 4, 5]
L2 = [1, 2, 3]
L3 = [x1 + x2 for (x1, x2) in list(zip(L1, L2))]
print(L3)

# Output: [4, 6, 8]


# Or, using map and not unpacking the tuple (our online environment has trouble with unpacking the 
# tuple in a lambda expression):

L1 = [3, 4, 5]
L2 = [1, 2, 3]
L3 = map(lambda x: x[0] + x[1], zip(L1, L2))
print(L3)

# Output: [4, 6, 8]


# Consider a function called possible, which determines whether a word is still possible to play in a 
# game of hangman, given the guesses that have been made and the current state of the blanked word.
# Below we provide function that fulfills that purpose

def possible(word, blanked, guesses_made):
    if len(word) != len(blanked):
        return False
    for i in range(len(word)):
        bc = blanked[i]
        wc = word[i]
        if bc == '_' and wc in guesses_made:
            return False
        elif bc != '_' and bc != wc:
            return False
    return True

print(possible("wonderwall", "_on__r__ll", "otnqurl"))
print(possible("wonderwall", "_on__r__ll", "wotnqurl"))

# Output:
# True
# False


# *** However, we can rewrite that using zip, to be a little more comprehensible. ***

def possible(word, blanked, guesses_made):
    if len(word) != len(blanked):
        return False
    for (bc, wc) in zip(blanked, word):
        if bc == '_' and wc in guesses_made:
            return False
        elif bc != '_' and bc != wc:
            return False
    return True

print(possible("wonderwall", "_on__r__ll", "otnqurl"))
print(possible("wonderwall", "_on__r__ll", "wotnqurl"))

# Output:
# True
# False



# 1. Below we have provided two lists of numbers, L1 and L2. Using zip and list comprehension,
#  create a new list, L3, that sums the two numbers if the number from L1 is greater than 10 and 
# the number from L2 is less than 5. This can be accomplished in one line of code.

L1 = [1, 5, 2, 16, 32, 3, 54, 8, 100]
L2 = [1, 3, 10, 2, 42, 2, 3, 4, 3]

L3 = [x1 + x2 for (x1, x2) in zip(L1, L2) if x1 > 10 and x2 < 5]
print(L3)

# Outpu: [18, 57, 103]