[Python] How to change character string (str) data to date (strptime of datetime)

[For beginners] How to change python string (str) data to date (datetime strptime)

The date data scraped on the WEB is a character string (str).

Convert the character string to date in order to store the acquired data in DB as date data.

manner

Use the strptime method of the datetime module.

python

import datetime as dt

No definition

import datetime

datetime.datetime.now()
#It is necessary to describe the module name at the beginning in full

With definition

import datetime

dt.datetime.now()
#The module name at the beginning can be abbreviated

• If the character string is a variable, the quotation mark of A is not required.

** How to use strptime ('A','B') ** -Match "A character string" and "B format".

Example 1(0 not filled)

A：「2019-1-9」
B：「%Y-%m-%d」

dt.datetime.strptime('2019-1-9','%y-%m-%d')

#output
datetime.datetime(2019, 1, 9, 0, 0)

% Y: 4 digits in the Christian era % m: Month (character string month is padded with 0 or not) % d: Day (character string month is padded with 0 or not)

Example 2(0 padded)

A：「19-05-08」
B：「%y-%m-%d」

dt.datetime.strptime('19-05-08','%y-%m-%d')

#output
datetime.datetime(2019, 5, 8, 0, 0)

% y: 2 digits (lowercase) % m,% d: 0 Supports both with and without padding

Example 3(date)

A: "May 8, 2019"
B：「%Y year%m month%d day "

dt.datetime.strptime('May 8, 2019','%Y year%m month%d day')

#output
datetime.datetime(2019, 5, 8, 0, 0)

Example 4(Correspondence between character strings and numerical values)

A: "Tomorrow's date is May 8th. The year is 2019."
B: "Tomorrow's date is%m month%d days. Year is%Y year "

dt.datetime.strptime('Tomorrow's date is May 8th. Year is 2019','Tomorrow's date%m month%d days. Year is%Y year')

#output
datetime.datetime(2019, 5, 8, 0, 0)

・ Dates are not in order -Just specify which number will be the date data

Example 5(variable)

A：「past」:'2019/3/23'
B：「%Y/%m/%d」

past= '2019/3/23'
dt.datetime.strptime(past,'%Y/%m/%d')

#output
datetime.datetime(2019, 3, 23, 0, 0)

• Variables do not require quotation marks.

Error when quoting variables ValueError: time data 'past' does not match format '%Y/%m/%d'

Example 6(Time,Minutes,Including seconds)

A：「future」:'March 23, 2030 5:21:42 123456 microseconds'
B：「%Y year%m month%d day%H o'clock%M minutes%S seconds%f microseconds "

past= '2019/3/23'
dt.datetime.strptime(future, '%Y year%m month%d day%H o'clock%M minutes%S seconds%f microseconds')

#output
datetime.datetime(2030, 3, 23, 5, 21, 42, 123456)

% H: Time (24-hour notation) % M: minutes % S: seconds % f: microseconds

code

dt.datetime.now()

#output
# datetime.datetime(2020, 3, 23, 0, 18, 1, 735003)

The meaning of each

In the first place, it was a mistake to think that "datetime.datetime.now ()" was divided into three parts, "①datetime", "②.datetime", and "③now ()".

Correctly, it is divided into two parts, "(1) datetime.datetime" and "(2) now ()".

Objects and methods

The syntax for using the method is object . method, so it looks like this:

Object: ① datetime.datetime Method: ② now ()

object

Put an entity in the object.

** ** -Substituted variable (eg a = 3) -Instance (materialized class)

→ datetime.datetime is an instance

Datetime instance (class) type

It's hard to understand if you just look at "datetime.datetime", but there are other types.

datetime.date: date datetime.time: time datetime.timedelta: difference datetime.tzinfo: Time zone information

Such

What is being done

▶「datetime.datetime.now()」 datetime.datetime is a collection of functions related to" date and time ". The now () method calls the now () function defined in datetime.datetime.

▶「datetime.date.now()」 ** Error **. datetime.date is a collection of functions related to" time ". The function now () is not defined in this.

▶「datetime.time.today()」 You can use this. A function called today () is defined in the class of datetime.date.

Summary

--Multiple classes are defined in the datetime module. --Specify the class with the data you want to handle (date, time, both? Etc.) --Class (instance) specification: datetime.AAAA --The methods defined for each class are different. --Use the method that suits each class: datetime.AAAA.BBBB ()

datetime.time.today() datetime.datetime.today()