遍历python中的两个列表

Question

I have two different lists, one has a set of days (70) and the other has 3 names. I would like to assign a name to every 7 days, and thought this was the way to do so, but now it only assigns one name to every date.

date_list is a list of 70 days and names contains 3 different names.

How can I fix this?

    date_dict = {}
    sum_names = len(names)
    counter = 0

for date in date_list:
                # If counter is sum of names, reset counter to 0
                if (counter == sum_names):
                        counter = 0

                # Else increment counter and add dictionary key/value        
                else:
                        date_dict[date] = names[counter]
                        counter += 1


print(date_dict)

Answer 1

If you take your list of three names and turn it into a list of 3x7 names, you can just cycle over it.

So starting with:

names = ['Donald', 'Ricky', 'Morty']

# Three * 7 names:
groups = [word for entry in names for word in [entry]*7]
# ['Donald','Donald','Donald',...'Ricky', 'Ricky', ... 'Morty']

With that you can just zip the cycle and dates:

from datetime import datetime, timedelta
from itertools import cycle

# a list of 70 dates
today = datetime.today()
date_list = [(today + timedelta(days=x)).strftime('%Y-%m-%d') for x in range(70)]

names = ['Donald', 'Ricky', 'Morty']
groups = [word for entry in names for word in [entry]*7]

# zip with cycle for a dict (or any other structure you want):
{date: name for date, name in zip(date_list, cycle(groups))}

Which will give you:

{'2022-02-15': 'Donald',
 '2022-02-16': 'Donald',
 '2022-02-17': 'Donald',
 '2022-02-18': 'Donald',
 '2022-02-19': 'Donald',
 '2022-02-20': 'Donald',
 '2022-02-21': 'Donald',
 '2022-02-22': 'Ricky',
 '2022-02-23': 'Ricky',
 '2022-02-24': 'Ricky',
 '2022-02-25': 'Ricky',
 ...
 '2022-04-17': 'Morty',
 '2022-04-18': 'Morty',
 '2022-04-19': 'Donald',
 '2022-04-20': 'Donald',
 '2022-04-21': 'Donald',
 '2022-04-22': 'Donald',
 '2022-04-23': 'Donald',
 '2022-04-24': 'Donald',
 '2022-04-25': 'Donald'}

Answer 2

By using extended slicing you can split your list into every nth interval (ie every seventh day).

In your case this can be done in the following way:

every_seventh_day = date_list[::7]
>> [day0, day7, day14, etc..]

You can then adjust your code in the following way:

for date in every_seventh_day:
                # If counter is sum of names, reset counter to 0
                if (counter == sum_names):
                        counter = 0

                date_dict[date] = names[counter]
                counter += 1

ps. The current implementation of the else statement will skip the iteration of counter=0 and names[0] will never be assigned a date. - unless this is intended for your use case it should be safe to remove:)

You can read more about slicing from the docs, specifically this example. https://python-reference.readthedocs.io/en/latest/docs/brackets/slicing.html#example-3

Edit: Solution 2 : The following solution Loops through each day progressively reducing the date_list size until empty,

In each iteration it updates date_dict with the next 7 days from the date_list as keys and with the name[counter] as the value.

It then increments the name counter value and checks if it needs to be reset. Additionally also checks if there are seven days for the next person else give them the remainder.

date_dict = {}
date_list= ["2022-02-16", "2022-02-17", "2022-02-18", etc..]
names = ["Donald", "Rick"]
counter = 0

while len(date_list) > 0:
    date_dict.update(dict.fromkeys([date_list.pop(0) for _ in range(7)], names[counter]))
    counter +=1
    if counter == len(names):
        counter = 0
    # Safety check if the list doesnt have at least 7 dates for the next iteration
    if len(date_list) < 7:
        date_dict.update(dict.fromkeys([date_list.pop(0) for _ in range(len(date_list))], names[counter]))

Answer 3

Having two counters for keeping track of the dates and names should work.

    date_dict = {}
    sum_names = len(names)
    date_len = 7
    date_counter = 0
    name_counter = 0

for date in date_list:
                # If date counter has hit 7 days then reset date counter and increment name_counter
                if (date_counter == date_len):
                        date_counter = 0
                        #if the name_counter has hit the sum of names then reset else increment
                        if(name_counter == sum_names):
                          name_counter=0
                        else:
                          name_counter+=1

                # Else increment counter and add dictionary key/value        
                else:
                        date_dict[date] = names[name_counter]
                        date_counter += 1