[Python] Class type and usage of datetime module

[Note] Class type and usage of python datetime module

Check the types and differences of classes that can be used in the datetime module of python with an example.

Official site

Class type

6 types of classes (data types) are available

1. datetime.date: Date (year, month, day)
2. datetime.time: Time (hours, minutes, seconds, microseconds)
3. datetime.datetime: date + time
4. datetime.timedelta: time difference
5. datetime.timezone: Time zone setting
6. datetime.tzinfo: Time zone information

Contents of each class

0. Supplementary conditions

Call the datetime module as dt.

Call the datetime module

import datetime as dt

▼ Actual usage example datetime.date is written as dt.date

• Datetime.datetime.date will result in an error （name 'datetime' is not defined）

1. datetime.date

Execution result of dt.date.today () datetime.date(2020, 3, 18) └ datetime.date type └ (2020, 3, 18) = (year, month, day)

⇒ ** You can get 3 data of year, month and day **. (Attributes: year, month, day)

--dt.time.now (): error --dt.time.today (): Error

type object 'datetime.time' has no attribute 'today'

** ■ How to use ** Specify the time yourself.

This is effective when you do not need date data and want to call or change only time data.

--Specify hours, minute, second, microsecond individually of datetime.time type. --Call the specified data. (Example: .hour) --Change the specified data (Example: .replace (hour = 1))

Specified number

Specifying and calling the time (datetime).time）

#Set the time
timeA = dt.time(10, 30, 45, 123456) 

#Call the time
timeA.hour  #Execution result: 10
timeA.minute #Execution result: 30
timeA.second #Execution result: 45
timeA.microsecond #Execution result: 123456

Change the time (replace)()）

#Set the time
timeA = dt.time(10, 30, 45, 123456) 

#(1)Change individually
timeA = timeA.replace(hour=5)  
timeA

#Execution result
# →　datetime.time(5, 30, 45, 123456) 


#(2)Change all at once
timeA = timeA.replace(hour=1, minute=2, second=30, microsecond=400)
timeA

#Output result
# → datetime.time(1, 2, 30, 400)

Execution result of dt.datetime.today () datetime.datetime(2020, 3, 18, 7, 42, 54, 95450) └ datetime.datetime type 　 └ (2020, 3, 18, 7, 42, 54, 95450) (Year, month, day, hour, minute, second, microsecond)

⇒ ** You can get 7 data of year, month, day, hour, minute, second, and microsecond **. (Attributes: year, month, day, hour, minute, microsecond)

• I also have tzinfo (tz: time zone information) on the back side.

** ▼ tzinfo (tz: time zone information) ** Information is output when the method is executed with now without parentheses.

Display time zone information

dt.datetime.now
<function datetime.now(tz=None)>

Frequently used methods now and today

#.now()
dtNow = dt.datetime.now()
dtNow  #datetime.datetime(2020, 3, 18, 21, 28, 13, 409431)

#.today()
dtToday = dt.datetime.today()
dtToday #datetime.datetime(2020, 3, 18, 22, 45, 10, 518281)

Frequently used method combine

#.combine(A, B)
dateA = dt.date(2020,5,6)
timeA = dt.time(10,20,0)

dt.datetime.combine(dateA, timeA)

#Output result
# → datetime.datetime(2020, 5, 6, 10, 30, 0)

• Combine (A, B) is determined to be ʻA = datetime.date typeandB = datetime.time type`.

If it is different from the specified type such as cobmbine (timeA, dateB), an error will occur.

combine() argument 1 must be datetime.date, not datetime.time

replace

#.replace()

dtNow =dt.datetime.now() 
dtNow # datetime.datetime(2020, 3, 18, 22, 10, 15, 517216)

dtNow = dtNow.replace(year=2018)
dtNow = dtNow.replace(hour=5, minute=30, second=30)
dtNow

#Output result
# → datetime.datetime(2018, 3, 18, 5, 30, 30, 474609)

** ■ Output the day of the week ** weekday (): 0-6 (Monday 0-Sunday 6) ʻIsoweekday ()`: 1-6 (Monday 1-Sunday 7)

Day of the week output

today = dt.datetime.today()  #datetime.datetime(2020, 3, 18, 22, 30, 46, 646567)

#.weekday()
today.weekday() #Output: 2 → Wednesday

#.isoweekday()
today.weekday() #Output: 3 → Wednesday

** ■ Output only date or time ** date()　：year、month、day time()　：hour、minute、second、microsecond

Date / time output

now = dt.datetime.now()
#datetime.datetime(2020, 3, 18, 22, 35, 50, 177279)

#.time()
now.time() #Output: datetime.time(22, 38, 1, 997649)

#.date()
now.date() #datetime.date(2020, 3, 18)

--Timedelta does not add or subtract. -** ★ Specify which item to add / subtract how many ** --dt.timedelta (days = 2): Add 2 days --dttimedelta (hours = -5): subtract 5 hours --Specifiable arguments (7 types. ** * Plural ** --weeks (: multiple of 7days) - days - hours - minutes - seconds - milliseconds - microseconds --Arguments that cannot be specified (** year and month are not possible **) - years - months --Default argument is 0

Unspecified arguments or incorrect arguments (singular, etc.) will result in an error

'years' is an invalid keyword argument for __new__()

** How to use ** (1) Add 2 weeks to January 1, 2020 + dt.timedelta(weeks=2)

Add with timedelta

newyear = dt.datetime(2020, 1, 1)  #Define January 1, 2020 as datetime type
newyear + dt.timedelta(weeks=2)

#Execution result
#datetime.datetime(2020, 1, 15, 0, 0)
#→ January 15, 2020

Subtract with timedelta

newyear = dt.datetime(2020, 1, 1)  #Define January 1, 2020 as datetime type
newyear + dt.timedelta(hours=-25)

#Execution result
datetime.datetime(2019, 12, 30, 23, 0)
#→ December 30, 2019 23:00

** ▼ Example ** -No error occurs even if time is added to date type (which does not have time data). ・ The calculated result is displayed. └ Calculated in the hidden part

Handling of data that the mold does not have

newyear2 = dt.date(2020, 1, 1)　　#datetime.date type (does not have time data)
newyear2 + dt.timedelta(hours=100) #Add 100 hours

#Execution result
#datetime.date(2020, 1, 5)
#→ January 5, 2020

--The types that can be used are datetime.datetime and datetime.date. --datetime.time cannot be used --The ones to compare need to be the same --Error occurs with datetime.datetime and datetime.date --Cannot add (error)

Find the interval between two dates (Case 1)

dateA = dt.date(2020,1,1)
dateB = dt.date(2020,1,9)

dateA - dateB  #Output: datetime.timedelta(days=-8)
dateB - dateA  #Output: datetime.timedelta(days=8)

Find the interval between two dates(Case 2)

pastA = dt.datetime(2000, 1, 1)
now = dt.datetime.now()  #Output: datetime.datetime(2020, 3, 18, 22, 56, 50, 604259)

now - pastA

#Output result
#datetime.timedelta(days=7382, seconds=82358, microseconds=594717)

• There are no years or months in datetime.timedelta

Addition is an error (* "+" is not supported)

unsupported operand type(s) for +

dt.timezone(dt.timedelta(hours=AAA), 'BBB')

There are two values to set.

--AAA: How much does it deviate from the standard? -+/- 0 ~ 24 * 24 or less --24 is an error --BBB: Name given to the set time zone --Use as an argument when calling

** ▼ Setting method ** ① United Kingdom (UCT. Standard: +0 hours) [≒ GMT] datetime.timezone(datetime.timedelta(0), 'UCT')

② Toronto (EDT.-4) datetime.timezone(datetime.timedelta(-4), 'EST')

③ Japan (JST. +9) dt.timezone(dt.timedelta(hours=+9), 'JST')

** ▼ Example of actual usage ** Set the time in Toronto (EDT) and recall the current time.

How to use timezone(Toronto time)

EDT = dt.timezone(dt.timedelta(hours=-4),'EDT')
EDT　#Output: datetime.timezone(datetime.timedelta(days=-1, seconds=72000), 'EDT')

dt.datetime.now(EDT)

#Output result
# datetime.datetime(2020, 3, 18, 10, 34, 8, 685415, tzinfo=datetime.timezone(datetime.timedelta(days=-1, seconds=72000), 'EDT'))

** ① UTC: Coordinated Universal Time ** └ Current Coordinated Universal Time └ Calculated from the frequency of cesium atoms

** ② GMT: Greenwich Mean Time ** └ Past standard time └ Calculated from the measurement results of the Greenwich Observatory └ Greenwich is a city just south of London

-Neither is much different (UTC ≒ GMT) --British time --UK is the standard: hours = ± 0