Simple Python question with dictionaries and lists

Question

The goal of the function is to make a grade adjustment based off of a dictionary and list. For instance

def adjust_grades(roster, grade_adjustment) 
adjust_grades({'ann': 75, 'bob': 80}, [5, -5])

will return

{'ann': 80, 'bob': 75}

I just need a nudge in the right direction, I'm new to Python so I thought to put a nested for loop for each num in grade_adjustment but its not the right way.

• AmourK: You should try defining your dictionary as an OrderedDict. Or define your grade_adjustment as a dictionary: {'ann' : 5, 'bob' : -5 }
• buran: @J.Murray, That was true till 3.6. In 3.6 order preserving feature was considered implementation detail. In 3.7+ order-preserving feature is guaranteed
• Alexander: The grade_adjustment should also be a dictionary. Then, for name, adj in grade_adjustment.items(): roster[name] += adj
• J. Murray: @Buran Nice! Its a solid edition. I think that I'd still consider alternatives than rely on that (esp if you don't know what version of the interpreter the code may be executed via)
• Alexander: @Alexander That makes a lot of sense, unfortunately its a solution I cannot use for this assignment. It HAS to be a list.

Answer 1

Assuming Python 3.7 (ordered dicts) and the length of the adjustments match the length of the items in the dictionary, you can zip them together as follows:

for name, adjustment_amount in zip(roster, grade_adjustment):
 roster[name] += adjustment_amount
>>> roster
{'ann': 80, 'bob': 75}

• Alexander: Very simple and easy to follow solution -- thank you!

Answer 2

This is making several assumptions:

• the dictionary and the list have the same length (your final code should make sure they do)
• you are using a version of python in which the order of the dictionary keys is preserved (if not, you can make grade_adjustment a dictionary as well, as mentioned by other comments)

result = roster.copy()
for index, key in enumerate(roster):
 result[key] += grade_adjustment[index]

• Alexander: Ah! Very helpful, that makes a lot of sense. I will try this, thank you.

Answer 3

You can use

def adjust_grades(roster, grade_adjustment):
 for k, v in enumerate(grade_adjustment):
 roster[list(roster.keys())[k]] = roster[list(roster.keys())[k]] + v
 return roster

This gives output as you said {'ann': 80, 'bob': 75}

• Alexander: I will try this too, thank you so much for your help!

Answer 4

assuming 3.7 or ordered dict and equal length:

def adjust_grades(roster, grade_adjustment):
 return {key:value + adjustment for (key, value), adjustment in
 zip(roster.items(), grade_adjustment)}
print(adjust_grades({'ann': 75, 'bob': 80}, [5, -5]))