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‎29-generators.md‎

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# Python Generators
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**Video link:**
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**Video link:** [https://youtu.be/ebj4qZ8SyMU](https://youtu.be/ebj4qZ8SyMU)
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In this video, we learned how to create custom iterators in Python using generator functions.
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‎30-datetime.md‎

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# Python `datetime` module
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**Video link:**
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In this video, we learned about the `datetime` module to manipulate date and time in Python.
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**Programs in the Video**
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- [Get Current Date](#get-current-date)
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- [The datetime.date Class](#the-datetimedate-class)
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- [The datetime.time Class](#the-datetimetime-class)
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- [The datetime.datetime Class](#the-datetimedatetime-class)
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- [Getting current date and time](#getting-current-date-and-time)
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- [The datetime.timedelta Class](#the-datetimetimedelta-class)
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- [Python `strftime()` method](#python-strftime-method)
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- [Python `strptime()` method](#python-strptime-method)
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---
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## Get Current Date
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We can find the current local date using the `today()` method of the `date` class of the `datetime` module:
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```python
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import datetime as dt
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current_date = dt.date.today()
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print(current_date)
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```
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**Output**
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```
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2021-02-10
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```
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Similar to the `date` class, the `datetime` module has many other useful classes to work with date and time:
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* `date` class - to work with date
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* `time` class - to work with time
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* `datetime` class - combination of `date` and `time` classes
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---
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## The datetime.date Class
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The `date` class of the `datetime` module is used to create `date` objects that can store year, month and day.
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```python
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import datetime as dt
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date1 = dt.date(2021, 1, 21)
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print(date1)
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print("Year:", date1.year)
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print("Month:", date1.month)
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print("Day:", date1.day)
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```
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**Output**
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```
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2021-01-21
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Year: 2021
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Month: 1
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Day: 21
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```
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---
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## The datetime.time Class
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The `time` class of the `datetime` module is used to create `time` objects that can store time of day like hours, minutes, seconds, and microseconds.
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The time class takes in all optional integer arguments. By default all of them are `0`.
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- The first argument is hour from `0` to `24`
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- The second one is minutes from `0` to `60`
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- The third is seconds from `0` to `60`
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- The fourth is microsecond from `0` to `999999`
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```python
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import datetime as dt
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time1 = dt.time(10, 47, 20, 234566)
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print(time1)
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print("Hour:", time1.hour)
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print("Minute:", time1.minute)
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print("Second:", time1.second)
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print("Microsecond:", time1.microsecond)
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```
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**Output**
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```
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10:47:20.234566
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Hour: 10
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Minute: 47
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Second: 20
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Microsecond: 234566
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```
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>**Note:** If you want more control and functionalities on time, use the `time` module.
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---
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## The datetime.datetime Class
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The `datetime` class of the `datetime` module is used to create objects that contain all the information from a `date` object as well as a `time` object.
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```python
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import datetime as dt
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datetime_obj = dt.datetime(2021, 11, 28, 23, 55, 59)
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print(datetime_obj)
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print(datetime_obj.date())
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print(datetime_obj.time())
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```
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**Output**
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```
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2021-11-28 23:55:59
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2021-11-28
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23:55:59
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```
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Like with `date` and `time` objects, we can also access individual attributes like `year`, `month` and `hour` as previously discussed.
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---
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## Getting current date and time
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To get the current local date and time at once, we can use the `now()` method of the `datetime` object.
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```python
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import datetime as dt
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current_time = dt.datetime.now()
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print(current_time)
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```
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**Output**
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```
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2021-01-21 05:56:45.817533
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```
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---
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## The datetime.timedelta Class
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A timedelta object represents the difference between two dates or times.
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Let's find out the time difference between now and the next new year.
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```python
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import datetime as dt
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current_time = dt.datetime.now()
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next_new_year = dt.datetime(2022, 1, 1)
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time_remaining = next_new_year - current_time
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print(time_remaining)
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print(type(time_remaining))
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```
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**Output**
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```
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324 days, 13:31:29.981402
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<class 'datetime.timedelta'>
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```
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This `timedelta` object can also be added or subtracted from `datetime` objects to get new `datetime` objects.
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---
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## Python `strftime()` method
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The `strftime()` method returns a string representing date and time for the datetime object.
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There are many formats to write the date and time depending on your location.
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If you are in the US, you probably use the `mm-dd-yyyy` format while if you're in the UK you will generally use the `dd-mm-yyyy` format.
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The `strftime()` method allows us to display the date and time in a custom specific format.
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```python
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import datetime as dt
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current_datetime = dt.datetime.now()
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print(current_datetime)
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string_date = current_datetime.strftime("%A, %B %d, %Y")
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print(string_date)
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```
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**Output**
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```
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2021-01-21 06:20:19.627086
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Thursday, January 21, 2021
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```
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Here,
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- `%A` represents the weekday name i.e. `Thursday`
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- `%B` represents the month's full name
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- `%d` represents the day of the month
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- `%Y` represents the year
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There are many other format codes:
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| Directive | Meaning | Example |
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|-----------|-------------------------------------------|---------------------|
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| `%a` | Abbreviated weekday name | Sun, Mon, ... |
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| `%A` | Full weekday name | Sunday, Monday, ... |
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| `%w` | Weekday as a decimal number | 0, 1, ..., 6 |
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| `%d` | Day of the month as a zero-padded decimal | 01, 02, ..., 31 |
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| `%b` | Abbreviated month name | Jan, Feb, ..., Dec |
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| `%p` | Locale’s AM or PM | AM, PM |
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---
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## Python `strptime()` method
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The `strptime()` method converts strings to datetime objects.
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```python
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import datetime as dt
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date_string = "21 June, 2021"
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date_object = dt.datetime.strptime(date_string, "%d %B, %Y")
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print("date_object:", date_object)
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```
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**Output**
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```
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date_object: 2018-06-21 00:00:00
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```

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