I can not figure out how to take the year, day and week to return the month. Right now I am just trying to develop a Python Script that will do this. The goal after finishing this script is to use it for a Spark SQL Query to find the month since in my data I am given a day, year and week in each row.
As of now my python code looks like so. This code only works for the statement I have into the print(getmonth(2, 30 ,2018) returning 7. I have tried other dates and the output is only "None". I have tried variables also, but no success there.
import datetime
def month(day, week, year):
for month in range(1,13):
try:
date = datetime.datetime(year, month, day)
except ValueError:
iso_year, iso_weeknum, iso_weekday = date.isocalendar()
if iso_weeknum == week:
return date.month
print(getmonth(2, 30, 2018))
#iso_(year,weeknum,weekday) are the classes for ISO. Year is 1-9999, weeknum is 0-52 or 53, and weekday is 0-6
#isocaldenar is a tuple (year, week#, weekday)
I don't really understand your questions, but i think datetime will work... sorce: Get date from ISO week number in Python:
>>> from datetime import datetime
>>> day = 28
>>> week = 30
>>> year = 2018
>>> t = datetime.strptime('{}_{}_{}{}'.format(day,week,year,-0), '%d_%W_%Y%w')
>>> t.strftime('%W')
'30'
>>> t.strftime('%m')
'07'
>>>
A simpler solution can be created using the pendulum library. As in your code, loop through month numbers, create dates, compare the weeks for these dates against the desired date. If found halt the loop; if the date is not seen then exit the loop with, say, a -1.
>>> import pendulum
>>> for month in range(1,13):
... date = pendulum.create(2018, month, 28)
... if date.week_of_year == 30:
... break
... else:
... month = -1
...
>>> month
7
>>> date
<Pendulum [2018-07-28T00:00:00+00:00]>
Here is a brute force method that loops through the days of the year (It expects the day as Monday being 0 and Sunday being 6, it also returns the Month 0 indexed, January being 0 and December being 11):
import datetime
def month(day, week, year):
#Generate list of No of days of the month
months = [31,28,31,30,31,30,31,31,30,31,30,31]
if((year % 4 == 0 and year % 100 != 0) or year % 400 == 0): months[1] += 1
#ISO wk1 of the yr is the first wk with a thursday, otherwise it's wk53 of the previous yr
currentWeek = 1 if day < 4 else 0
#The day that the chosen year started on
currentDay = datetime.datetime(year, 1, 1).weekday()
#Loop over every day of the year
for i in range(sum(months)):
#If the week is correct and day is correct you're done
if day == currentDay and week == currentWeek:
return months.index(next(filter(lambda x: x!=0, months)))
#Otherwise, go to next day of wk/next wk of yr
currentDay = (currentDay + 1) % 7
if currentDay == 0:
currentWeek += 1
#And decrement counter for current month
months[months.index(next(filter(lambda x: x!=0, months)))]-=1
print(month(2, 30, 2018)) # 6 i.e. July
months.index(next(filter(lambda x: x!=0, months))) is used to get the first month of that we haven't used all of the days of, i.e. the month you're currently in.
If I have two dates (ex. '8/18/2008' and '9/26/2008'), what is the best way to get the number of days between these two dates?
If you have two date objects, you can just subtract them, which computes a timedelta object.
from datetime import date
d0 = date(2008, 8, 18)
d1 = date(2008, 9, 26)
delta = d1 - d0
print(delta.days)
The relevant section of the docs:
https://docs.python.org/library/datetime.html.
See this answer for another example.
Using the power of datetime:
from datetime import datetime
date_format = "%m/%d/%Y"
a = datetime.strptime('8/18/2008', date_format)
b = datetime.strptime('9/26/2008', date_format)
delta = b - a
print delta.days # that's it
Days until Christmas:
>>> import datetime
>>> today = datetime.date.today()
>>> someday = datetime.date(2008, 12, 25)
>>> diff = someday - today
>>> diff.days
86
More arithmetic here.
everyone has answered excellently using the date,
let me try to answer it using pandas
dt = pd.to_datetime('2008/08/18', format='%Y/%m/%d')
dt1 = pd.to_datetime('2008/09/26', format='%Y/%m/%d')
(dt1-dt).days
This will give the answer.
In case one of the input is dataframe column. simply use dt.days in place of days
(dt1-dt).dt.days
You want the datetime module.
>>> from datetime import datetime
>>> datetime(2008,08,18) - datetime(2008,09,26)
datetime.timedelta(4)
Another example:
>>> import datetime
>>> today = datetime.date.today()
>>> print(today)
2008-09-01
>>> last_year = datetime.date(2007, 9, 1)
>>> print(today - last_year)
366 days, 0:00:00
As pointed out here
from datetime import datetime
start_date = datetime.strptime('8/18/2008', "%m/%d/%Y")
end_date = datetime.strptime('9/26/2008', "%m/%d/%Y")
print abs((end_date-start_date).days)
It also can be easily done with arrow:
import arrow
a = arrow.get('2017-05-09')
b = arrow.get('2017-05-11')
delta = (b-a)
print delta.days
For reference: http://arrow.readthedocs.io/en/latest/
without using Lib just pure code:
#Calculate the Days between Two Date
daysOfMonths = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
def isLeapYear(year):
# Pseudo code for this algorithm is found at
# http://en.wikipedia.org/wiki/Leap_year#Algorithm
## if (year is not divisible by 4) then (it is a common Year)
#else if (year is not divisable by 100) then (ut us a leap year)
#else if (year is not disible by 400) then (it is a common year)
#else(it is aleap year)
return (year % 4 == 0 and year % 100 != 0) or year % 400 == 0
def Count_Days(year1, month1, day1):
if month1 ==2:
if isLeapYear(year1):
if day1 < daysOfMonths[month1-1]+1:
return year1, month1, day1+1
else:
if month1 ==12:
return year1+1,1,1
else:
return year1, month1 +1 , 1
else:
if day1 < daysOfMonths[month1-1]:
return year1, month1, day1+1
else:
if month1 ==12:
return year1+1,1,1
else:
return year1, month1 +1 , 1
else:
if day1 < daysOfMonths[month1-1]:
return year1, month1, day1+1
else:
if month1 ==12:
return year1+1,1,1
else:
return year1, month1 +1 , 1
def daysBetweenDates(y1, m1, d1, y2, m2, d2,end_day):
if y1 > y2:
m1,m2 = m2,m1
y1,y2 = y2,y1
d1,d2 = d2,d1
days=0
while(not(m1==m2 and y1==y2 and d1==d2)):
y1,m1,d1 = Count_Days(y1,m1,d1)
days+=1
if end_day:
days+=1
return days
# Test Case
def test():
test_cases = [((2012,1,1,2012,2,28,False), 58),
((2012,1,1,2012,3,1,False), 60),
((2011,6,30,2012,6,30,False), 366),
((2011,1,1,2012,8,8,False), 585 ),
((1994,5,15,2019,8,31,False), 9239),
((1999,3,24,2018,2,4,False), 6892),
((1999,6,24,2018,8,4,False),6981),
((1995,5,24,2018,12,15,False),8606),
((1994,8,24,2019,12,15,True),9245),
((2019,12,15,1994,8,24,True),9245),
((2019,5,15,1994,10,24,True),8970),
((1994,11,24,2019,8,15,True),9031)]
for (args, answer) in test_cases:
result = daysBetweenDates(*args)
if result != answer:
print "Test with data:", args, "failed"
else:
print "Test case passed!"
test()
For calculating dates and times, there are several options but I will write the simple way:
from datetime import timedelta, datetime, date
import dateutil.relativedelta
# current time
date_and_time = datetime.now()
date_only = date.today()
time_only = datetime.now().time()
# calculate date and time
result = date_and_time - timedelta(hours=26, minutes=25, seconds=10)
# calculate dates: years (-/+)
result = date_only - dateutil.relativedelta.relativedelta(years=10)
# months
result = date_only - dateutil.relativedelta.relativedelta(months=10)
# week
results = date_only - dateutil.relativedelta.relativedelta(weeks=1)
# days
result = date_only - dateutil.relativedelta.relativedelta(days=10)
# calculate time
result = date_and_time - timedelta(hours=26, minutes=25, seconds=10)
result.time()
Hope it helps
There is also a datetime.toordinal() method that was not mentioned yet:
import datetime
print(datetime.date(2008,9,26).toordinal() - datetime.date(2008,8,18).toordinal()) # 39
https://docs.python.org/3/library/datetime.html#datetime.date.toordinal
date.toordinal()
Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d,
date.fromordinal(d.toordinal()) == d.
Seems well suited for calculating days difference, though not as readable as timedelta.days.
from datetime import date
def d(s):
[month, day, year] = map(int, s.split('/'))
return date(year, month, day)
def days(start, end):
return (d(end) - d(start)).days
print days('8/18/2008', '9/26/2008')
This assumes, of course, that you've already verified that your dates are in the format r'\d+/\d+/\d+'.
Here are three ways to go with this problem :
from datetime import datetime
Now = datetime.now()
StartDate = datetime.strptime(str(Now.year) +'-01-01', '%Y-%m-%d')
NumberOfDays = (Now - StartDate)
print(NumberOfDays.days) # Starts at 0
print(datetime.now().timetuple().tm_yday) # Starts at 1
print(Now.strftime('%j')) # Starts at 1
If you want to code the calculation yourself, then here is a function that will return the ordinal for a given year, month and day:
def ordinal(year, month, day):
return ((year-1)*365 + (year-1)//4 - (year-1)//100 + (year-1)//400
+ [ 0,31,59,90,120,151,181,212,243,273,304,334][month - 1]
+ day
+ int(((year%4==0 and year%100!=0) or year%400==0) and month > 2))
This function is compatible with the date.toordinal method in the datetime module.
You can get the number of days of difference between two dates as follows:
print(ordinal(2021, 5, 10) - ordinal(2001, 9, 11))
Without using datetime object in python.
# A date has day 'd', month 'm' and year 'y'
class Date:
def __init__(self, d, m, y):
self.d = d
self.m = m
self.y = y
# To store number of days in all months from
# January to Dec.
monthDays = [31, 28, 31, 30, 31, 30,
31, 31, 30, 31, 30, 31 ]
# This function counts number of leap years
# before the given date
def countLeapYears(d):
years = d.y
# Check if the current year needs to be considered
# for the count of leap years or not
if (d.m <= 2) :
years-= 1
# An year is a leap year if it is a multiple of 4,
# multiple of 400 and not a multiple of 100.
return int(years / 4 - years / 100 + years / 400 )
# This function returns number of days between two
# given dates
def getDifference(dt1, dt2) :
# COUNT TOTAL NUMBER OF DAYS BEFORE FIRST DATE 'dt1'
# initialize count using years and day
n1 = dt1.y * 365 + dt1.d
# Add days for months in given date
for i in range(0, dt1.m - 1) :
n1 += monthDays[i]
# Since every leap year is of 366 days,
# Add a day for every leap year
n1 += countLeapYears(dt1)
# SIMILARLY, COUNT TOTAL NUMBER OF DAYS BEFORE 'dt2'
n2 = dt2.y * 365 + dt2.d
for i in range(0, dt2.m - 1) :
n2 += monthDays[i]
n2 += countLeapYears(dt2)
# return difference between two counts
return (n2 - n1)
# Driver program
dt1 = Date(31, 12, 2018 )
dt2 = Date(1, 1, 2019 )
print(getDifference(dt1, dt2), "days")
If you don't have a date handling library (or you suspect it has bugs in it), here's an abstract algorithm that should be easily translatable into most languages.
Perform the following calculation on each date, and then simply subtract the two results. All quotients and remainders are positive integers.
Step A. Start by identifying the parts of the date as Y (year), M (month) and D (day). These are variables that will change as we go along.
Step B. Subtract 3 from M
(so that January is -2 and December is 9).
Step C. If M is negative, add 12 to M and subtract 1 from the year Y.
(This changes the "start of the year" to 1 March, with months numbered 0 (March) through 11 (February). The reason to do this is so that the "day number within a year" doesn't change between leap years and ordinary years, and so that the "short" month is at the end of the year, so there's no following month needing special treatment.)
Step D.
Divide M by 5 to get a quotient Q₁ and remainder R₁. Add Q₁ × 153 to D. Use R₁ in the next step.
(There are 153 days in every 5 months starting from 1 March.)
Step E. Divide R₁ by 2 to get a quotient Q₂ and ignore the remainder. Add R₁ × 31 - Q₂ to D.
(Within each group of 5 months, there are 61 days in every 2 months, and within that the first of each pair of months is 31 days. It's safe to ignore the fact that Feb is shorter than 30 days because at this point you only care about the day number of 1-Feb, not of 1-Mar the following year.)
Steps D & E combined - alternative method
Before the first use, set L=[0,31,61,92,122,153,184,214,245,275,306,337]
(This is a tabulation of the cumulative number of days in the (adjusted) year before the first day of each month.)
Add L[M] to D.
Step F
Skip this step if you use Julian calendar dates rather than Gregorian calendar dates; the change-over varies between countries, but is taken as 3 Sep 1752 in most English-speaking countries, and 4 Oct 1582 in most of Europe.
You can also skip this step if you're certain that you'll never have to deal with dates outside the range 1-Mar-1900 to 28-Feb-2100, but then you must make the same choice for all dates that you process.
Divide Y by 100 to get a quotient Q₃ and remainder R₃. Divide Q₃ by 4 to get another quotient Q₄ and ignore the remainder. Add Q₄ + 36524 × Q₃ to D.
Assign R₃ to Y.
Step G.
Divide the Y by 4 to get a quotient Q₅ and ignore the remainder. Add Q₅ + 365 × Y to D.
Step H. (Optional)
You can add a constant of your choosing to D, to force a particular date to have a particular day-number.
Do the steps A~G for each date, getting D₁ and D₂.
Step I.
Subtract D₁ from D₂ to get the number of days by which D₂ is after D₁.
Lastly, a comment: exercise extreme caution dealing with dates prior to about 1760, as there was not agreement on which month was the start of the year; many places counted 1 March as the new year.