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Modules and Packages

--- ## Lesson Objectives *After this lesson, you will be able to...* * Add packages and modules to a Python program. * Create a program utilizing PyTime. * Navigate library documentation. --- ## Discussion: Let's Dive In Do you remember `itertools`? What do you think these have in common? - `itertools`. - A Python function that tells us when Mother's Day is. - A Python function that gets all the contents of a webpage for us. --- ## What is a Module? Answer: They're all available to us via modules! (In fact, `itertools` IS a module). Modules are collections of useful Python code and functions that we can use. - This is much like a class that someone else has written. - It's free - less work for us! Use a function by `import ` at the top of your code, then `.function_you_want()`. ```python # import < module name > - brings in the module file, so we can use it. import itertools food = ['pizza', 'tacos', 'sushi'] colors = ['red', 'green'] # itertools.chain : "Look in the itertools module, and use the chain function" chained_list = list(itertools.chain(food, colors)) ``` **Pro Tip**: Check the Additional Reading at the end of the lesson to see how to write your own module! --- ## Python Standard Library We're going to look at several different modules to get you used to them. The [Python Standard Library](https://docs.python.org/3/library/) bundles all common modules, so we can just `import` (use) them. We've seen the `itertools` module already. Let's look at another module, `random`: ```python import random # Done! Now we can use any functions in the random module! # randint is a function in the random module my_random_number = random.randint(2,8) # This could be 2, 3, 4, 5, 6, 7, or 8 print(my_random_number) ``` --- ## We Do: Let's Import Random Run the code in the repl below. What happened? Why? Uncomment the first line: `import random`. Run it again. Try changing the values.

**Teaching Tips**: - Use this as a teaching aid, not an exercise. - Demonstrate how to import a module. - Point out what happens when we forget the import statement. - Show the correct way to use the basic `randint` function. - Demonstrate **Talking Points**: - Post-activity: "Importing the module tells your program that the module exists - there are thousands of modules, so to save space, your program will only use the ones you tell it to." - "You may have noticed a NameError. That means it doesn't know what module you're referring to since it wasn't imported." different values for the randint function as a short "we do" activity. Show a large range and a small range. **Repl.it Note**: ```python # import random # Done! Now we can use the random module all we want! # randint is a function in the random module my_random_number = random.randint(2,8) # This could be 2, 3, 4, 5, 6, 7, or 8 print(my_random_number) ```

--- ## We do: Exploring the Random Module How do we know: - What `randint` does? - What the `random` module has? Every module has documentation, which has: - What functions are in the module. - How to use them. Here is the documentation for the random module. - Can you find our `randint` function? --- ## Partner Exercise: Random Numbers Get with a partner and pick a driver! Together: - Find the `random` function in the documentation. (Yes, a function can have the same name as the module). - Print out a randomly generated number using `random()`. - Run the program several times; is your random number different every time? * Why do you think this is useful? > **Protip**: The `[`, in mathematics means `inclusive`, whereas the `)` means `exclusive`. Thus the possible values include 0.0, but do **not** include 1.0! --- ## Quick Review Modules are collections of useful Python code and functions that we can use. Use a function by `import ` at the top of your code, then `.function_you_want()`. We've looked at two modules: `itertools` and `random`. ```python # Import statements go at the top of your file import itertools import random # Using the randint function in the random module my_random_number = random.randint(2,8) print(my_random_number) # Using the chain function in the intertools module food = ['pizza', 'tacos', 'sushi'] colors = ['red', 'green'] chained_list = list(itertools.chain(food, colors)) ``` The [Python Standard Library](https://docs.python.org/3/library/) bundles all common modules, so we can just `import` (use) them. **Next up:** More `random` module practice. --- ## We Do: Do You Feel Lucky? How could you pick a random value from a list? The `random` module has a function called `choice` - it works on any non-empty list. ```python people_in_lottery = ["Tina", "Batu", "Gina", "Jim", "Andres"] lottery_winner = random.choice(people_in_lottery) print(lottery_winner, "wins a new car!") # Gina ``` Let's try.

**Talking Points**: - "Let's switch gears a little bit. Random numbers are nice, but sometimes we have a list and we just want to pick a random item on that list. Suppose we run a lottery. We have a list of everyone who bought a lottery ticket and the winner will get a new car. How can we pick a winner?" **Teaching Tips**: - Ask the students to change the names to the people sitting around them. If you have a shy class, this gets people talking. - Try changing the list to hold numbers and other elements. **Repl.it Note**: ```python import random # Directions # - Replace the names with your name and 4 nearby classmates. # - Run the program # - Who won the car? # Create a list of candidates people_in_lottery = [] # This is selecting one winner lottery_winner = random.choice(people_in_lottery) # This announces the winner! print(lottery_winner, "wins a new car!") ```

--- ## Partner Exercise: Let's Get Random! Get with a partner and create a local file, `random_test.py` - Generate a random number with `random.randrange()`. Print it out. - Create a list, like `deck = ["ten", "jack", "queen", "king", "ace"]` - Use `random.choice()` to pick a random card in your deck. Print it out. - Use `random.shuffle()` to mix up your deck; print that out. Here is the documentation for the random module, so you can look up functions. --- ## Random Solution --- ## Quick Review Modules are collections of useful Python code and functions that we can use. Use a function by `import ` at the top of your code, then `.function_you_want()`. The [Python Standard Library](https://docs.python.org/3/library/) bundles all common modules, so we can just `import` (use) them. `itertools` and `random` are modules inside the Python Standard Library. ```python # Import statements go at the top of your file - they import straight from the Python Standard Library! import itertools import random # Using the randint function in the random module my_random_number = random.randint(2,8) print(my_random_number) # Using the chain function in the intertools module food = ['pizza', 'tacos', 'sushi'] colors = ['red', 'green'] chained_list = list(itertools.chain(food, colors)) ``` --- ## What is a Package? A package, also called a **library**, is a place where one or more related modules are stored. - In technical terms, *one or more* modules bundled together under a single namespace. - A package is like a folder, while a module is like a file. The [Python Standard Library](https://docs.python.org/3/library/) bundles all common modules - it's the package with `itertools` and `random` modules inside it. **All packages are modules, but not all modules are packages.** --- ## We Do: ModuleNotFoundError The Python Standard Library has a [huge list](https://docs.python.org/3/library/index.html) of modules. But not every Python module in the world is part of it! `pytime` is a non-standard module. PyTime can: * Get dates, date ranges, and times. * Find the date of a particular holiday. Create a new file called `pytime_test.py`. Put this line in it and run it: ```python import pytime ``` What's happened? `ModuleNotFoundError`: - The module isn't part of the standard library. - If we want to use modules from other packages, we'll have to tell Python that those packages exist. --- ## Including PyTime When importing from the standard library, the package is implied: ```python # (from standard) import MODULE import random ``` Otherwise, you need to specify the package! ```python # from PACKAGE import MODULE from pytime import pytime # The names don't need to be the same: from pygame import joystick # Yes - that's real! ``` Change your file to read `from pytime import pytime`. Does it work? > **Protip**: Remember that *package* means *library*! --- ## Installing PyTime New packages need to be installed. - Let's install `pytime`. In your command prompt: ``` pip3 install pytime ``` Once that's successful, try again to run your file. > **Protip**: `pip` stands for `Pip Installs Packages`. `pip3` uses Python3. > Note: Repl.it is a great website for testing, because it automatically installs libraries for us. --- ## PyTime Holidays Let's explore PyTime: - Scan the PyTime docs, to find the `mother` function. When is Mother's Day? ```python # This gets mother's day of 2016 mothers_day = pytime.mother(2016) # 2016-05-08 ``` What about this year? ```python # This gets mother's day of this year mothers_day = pytime.mother() ``` Try these in your file to be sure you can call PyTime functions! --- ## PyTime Documentation Here are some examples of PyTime in action: ```python >>>pytime.father() # Father's Day without a year (defaults to current year, so this example was generated in 2015) datetime.date(2015, 6, 21) >>> >>>pytime.mother(2016) # 2016 Mother's Day datetime.date(2016, 5, 8) >>> >>>pytime.easter(1999) # 1999 Easter datetime.date(1999, 4, 4) ``` --- ## Quick Review Not all modules are in the standard library. If you try to import a module Python doesn't recognize, you'll get a `ModuleNotFoundError`. When importing from the standard library, the package is implied: ```python # (from standard) import MODULE import random ``` Otherwise, you need to specify the package! ```python # from PACKAGE import MODULE from pytime import pytime from pygame import joystick ``` If you're using a non-standard package like `pytime` or `pygame`, you'll have to also install it. You can use the website repl.it for testing small pieces of code - it has packages installed. **Up next**: Continuing exploring documentation. --- ## You Do: PyTime Festivals Look through the PyTime docs; can you find the `father` and `easter` functions? In your local file, pick a year. In that year, print the month and day of: * Mother's Day. * Father's Day. * Easter Sunday. --- ## PyTime Festivals: Solution --- ## We Do: The Grinch Who Stole Christmas? Why does the documentation only have 3 holidays? Time for some sleuthing! Most times, you only need to look at a module's documentation. However, sometimes the person that did the documenting didn't write everything down. Because a module is simply a `.py` file, we can view it. - Open up the project's [Github page](https://github.com/shinux/PyTime). - Look at the files and folders near the top of the page. - Click on the folder `pytime`. - Click on the file `pytime.py`. - Scroll down to the `Festivals` section at the bottom of the file. - What function do you see which would likely give you Christmas Day? --- ## You Do: Using the PyTime Module In your `pytime_test.py`: 1. Decide on a list of three holidays you like. - (e.g. Christmas, Halloween...) 1. Write a function that prompts a user for a year and a holiday. - (e.g. "Enter a year", then "Choose Christmas, Halloween, or Mother's Day") 1. Have your function print out the date of that holiday for that year. - (e.g. "In 2016, Mother's Day was on 2016-05-08") --- ## Summary and Q&A Modules are `.py` files with functions. They're written by other people for us to use! - A packages (a.k.a. library) is a bundle of one or more modules. - Python's standard library has a lot of common modules! `random`, `itertools`, etc. - Nonstandard libraries need to be installed (`pip3 install pytime`). To use modules, at the top of your file, put: ```python # From the standard library: `import MODULE` import random # From non-standard packages: `from PACKAGE import MODULE` from pytime import pytime from pygame import joystick # And preface your function with the module name. mothers_day = pytime.mother(2016) # 2016-05-08 ``` --- ## Additional Resources * [Python Modules](https://docs.python.org/3/tutorial/modules.html) * [Python's Standard Library](https://docs.python.org/3/library/index.html) * [Write a module in python 3 - Digital Ocean](https://www.digitalocean.com/community/tutorials/how-to-write-modules-in-python-3) * [Itertools](https://docs.python.org/3/library/itertools.html) * [Random](https://docs.python.org/3/library/random.html) * [PyTime](https://pypi.org/project/pytime/) * [List of Commonly Used Packages](https://pythontips.com/2013/07/30/20-python-libraries-you-cant-live-without/) * [Useful Modules by Discipline](https://wiki.python.org/moin/UsefulModules) * [Further Reading](https://www.learnpython.org/en/Modules_and_Packages) * [Formatting Datetime](https://docs.python.org/3.0/library/datetime.html#strftime-behavior)