Why do I have to use a global for imported variable?

September 2, 2022

import datetime
from datetime import date

def get_one_week():
    global date
    seven_dates = []
    date = date.today()
    for i in range(7):
        date += datetime.timedelta(days=-1)
        date_str = date.strftime('%Y%m%d')
        seven_dates.append(date_str)
    return seven_dates

print(get_one_week())

This will print out:

['20220901', '20220831', '20220830', '20220829', '20220828', '20220827', '20220826']

My question, both ‘date’ and ‘datetime’ are imported variables, but why do I have use a global declaration for the ‘date’ but not for the ‘datetime’ variable?

>Solution :

It’s because you declared your variable date so python thinks that you referenced the local variable before any assignment try change it to other name so it will use the global one

import datetime
from datetime import date

def get_one_week():
    seven_dates = []
    d = date.today()
    for i in range(7):
        d += datetime.timedelta(days=-1)
        date_str = d.strftime('%Y%m%d')
        seven_dates.append(date_str)
    return seven_dates
    
print(get_one_week())