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‎README.md‎

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> "The only way to learn a new programming language is by writing programs in it." - Dennis Ritchie
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I believe you can learn serious things through silly games. I also think you will learn best by *doing*. This is a book of programming exercises. Each chapter includes a description of a program you should write with examples of how the program should work. Most importantly, each program includes with a test suite so that you know if your program is working well enough.
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I believe you can learn serious things through silly games. I also think you will learn best by *doing*. This is a book of programming exercises. Each chapter includes a description of a program you should write with examples of how the program should work. Most importantly, each program includes tests so that you know if your program is working well enough.
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I won't necessarily show you beforehand what you need to write a program. I'll describe what the program should do and provide some discussion about how to write it. I'll also create an appendix with short examples of how to do things like how to use `argparse`, how to read/write from/to a file, how to process all the files in a directory, how to extract k-mers from a string, etc. I'll provide some building blocks, but I want you to figure out how to put the pieces together.
7+
I won't necessarily show you beforehand how to write each program. I'll describe what the program should do and provide some discussion about how to write it. I'll also create an appendix with short examples of how to do things like how to use `argparse`, how to read/write from/to a file, how to process all the files in a directory, how to extract k-mers from a string, etc. I'll provide some building blocks, but I want you to figure out how to put the pieces together.
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## Forking GitHub repo
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## new.py
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I provide a program in the `bin` directory called `new.py` that will help you stub out new Python programs using the `argparse` module to parse the command line arguments and options for your programs. I recommend you start every new program with this program. For example, in the `article` directory the `README.md` wants you to create a program called `article.py`. You should go into the directory with `cd article` and then do:
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I provide some useful programs in the `bin` directory including one called `new.py` that will help you stub out new Python programs using the `argparse` module to parse the command line arguments and options for your programs. I recommend you start every new program with this program. For example, in the `article` directory the `README.md` wants you to create a program called `article.py`. You should do this:
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````
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$ cd article
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$ new.py article
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````
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This will create a new file called `article.py` (that has been made executable with `chmod +x`, if your operating system supports that) that has example code for you to start writing your program. It's best to put `new.py` into your `$PATH` or alter your `$PATH` to include the directory where it's located. I usually create a `$HOME/.local/bin` that I add to my `$PATH` for programs like this.
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This will create a new file called `article.py` (that has been made executable with `chmod +x`, if your operating system supports that) that has example code for you to start writing your program.
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## $PATH
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Your `$PATH` is a list of directories where your operating system will look for programs. To see what your `$PATH` looks like, do:
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````
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$ echo $PATH
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````
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Probably each directory is separated by a colon (`:`). *The order of the directories matters!* For instance, it's common to have more than one version of Python installed. When you type `python` on the command line, the directories in your `$PATH` are searched in order, and the first `python` found is the one that is used (and it's probably Python version 2!)
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You could execute `new.py` by giving the full path to the program, e.g., `$HOME/work/playful_python/bin/new.py`, but that's really tedious. It's best to put `new.py` into one of the directories that is already in your `$PATH` like maybe `/usr/local/bin`. The problem is that you probably need administrator privileges to write to most of the directories that are in your `$PATH.`. If you are working on your laptop, this is probably not a problem, but if you are on a shared system, you probably won't be able to copy the program into your `$PATH` directories.
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An alternative is to alter your `$PATH` to include the directory where `new.py` is located. E.g., if `new.py` is in `$HOME/work/playful_python/bin/`, then add this directory to your `$PATH` -- probably by editing `.bashrc` or `.bash_profile` located in your `$HOME` directory (if you use `bash`). See the documentation for your shell of choice to understand how to edit and persist your `$PATH`.
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For what it's worth, I always create a `$HOME/.local` directory for local installations of software I need, so I add `$HOME/.local/bin` to my `$PATH`. Then I copy programs like `new.py` there and they are available to me anywhere on the system.
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## Testing your programs
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‎appendix/argparse/README.md‎

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files = foo, bar
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````
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## Choices
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Sometimes you want to limit the values of an argument. You can pass in a `list` of valid values to the `choices` option.
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````
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$ cat appendix/argparse/choices.py
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#!/usr/bin/env python3
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"""Choices"""
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import argparse
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parser = argparse.ArgumentParser(
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description='Choices',
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formatter_class=argparse.ArgumentDefaultsHelpFormatter)
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parser.add_argument('color', metavar='str', help='Color', choices=['red', 'yellow', 'blue'])
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args = parser.parse_args()
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print('color =', args.color)
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````
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Any value not present in the list will be rejected and the user will be shown the valid choices:
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````
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$ ./choices.py
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usage: choices.py [-h] str
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choices.py: error: the following arguments are required: str
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$ ./choices.py purple
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usage: choices.py [-h] str
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choices.py: error: argument str: invalid choice: 'purple' (choose from 'red', 'yellow', 'blue')
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````
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## Automatic help
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The `argparse` module reserves the `-h` and `--help` flags for generating help documentation. You do not need to add these nor are you allowed to use these flags for other purposes. Using the above definition, this is the help that `argparse` will generate:
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‎bin/compile.py‎

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solution_py = os.path.join(in_dir, dir_name, 'solution.py')
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if os.path.isfile(solution_py):
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print('\tSOLUTION PY')
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print('\tSOLUTION')
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fh.write('## Solution\n\n')
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fh.write('````\n')
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numbered = getoutput('cat -n {}'.format(solution_py))
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‎book.md‎

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> "The only way to learn a new programming language is by writing programs in it." - Dennis Ritchie
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I believe you can learn serious things through silly games. I also think you will learn best by *doing*. This is a book of programming exercises. Each chapter includes a description of a program you should write with examples of how the program should work. Most importantly, each program includes with a test suite so that you know if your program is working well enough.
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I believe you can learn serious things through silly games. I also think you will learn best by *doing*. This is a book of programming exercises. Each chapter includes a description of a program you should write with examples of how the program should work. Most importantly, each program includes tests so that you know if your program is working well enough.
99

10-
I won't necessarily show you beforehand what you need to write a program. I'll describe what the program should do and provide some discussion about how to write it. I'll also create an appendix with short examples of how to do things like how to use `argparse`, how to read/write from/to a file, how to process all the files in a directory, how to extract k-mers from a string, etc. I'll provide some building blocks, but I want you to figure out how to put the pieces together.
10+
I won't necessarily show you beforehand how to write each program. I'll describe what the program should do and provide some discussion about how to write it. I'll also create an appendix with short examples of how to do things like how to use `argparse`, how to read/write from/to a file, how to process all the files in a directory, how to extract k-mers from a string, etc. I'll provide some building blocks, but I want you to figure out how to put the pieces together.
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## Forking GitHub repo
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@@ -22,13 +22,30 @@ This will allow you to `git pull upstream master` in order to get updates. When
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## new.py
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I provide a program in the `bin` directory called `new.py` that will help you stub out new Python programs using the `argparse` module to parse the command line arguments and options for your programs. I recommend you start every new program with this program. For example, in the `article` directory the `README.md` wants you to create a program called `article.py`. You should go into the directory with `cd article` and then do:
25+
I provide some useful programs in the `bin` directory including one called `new.py` that will help you stub out new Python programs using the `argparse` module to parse the command line arguments and options for your programs. I recommend you start every new program with this program. For example, in the `article` directory the `README.md` wants you to create a program called `article.py`. You should do this:
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````
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$ cd article
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$ new.py article
2930
````
3031

31-
This will create a new file called `article.py` (that has been made executable with `chmod +x`, if your operating system supports that) that has example code for you to start writing your program. It's best to put `new.py` into your `$PATH` or alter your `$PATH` to include the directory where it's located. I usually create a `$HOME/.local/bin` that I add to my `$PATH` for programs like this.
32+
This will create a new file called `article.py` (that has been made executable with `chmod +x`, if your operating system supports that) that has example code for you to start writing your program.
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34+
## $PATH
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Your `$PATH` is a list of directories where your operating system will look for programs. To see what your `$PATH` looks like, do:
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38+
````
39+
$ echo $PATH
40+
````
41+
42+
Probably each directory is separated by a colon (`:`). *The order of the directories matters!* For instance, it's common to have more than one version of Python installed. When you type `python` on the command line, the directories in your `$PATH` are searched in order, and the first `python` found is the one that is used (and it's probably Python version 2!)
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You could execute `new.py` by giving the full path to the program, e.g., `$HOME/work/playful_python/bin/new.py`, but that's really tedious. It's best to put `new.py` into one of the directories that is already in your `$PATH` like maybe `/usr/local/bin`. The problem is that you probably need administrator privileges to write to most of the directories that are in your `$PATH.`. If you are working on your laptop, this is probably not a problem, but if you are on a shared system, you probably won't be able to copy the program into your `$PATH` directories.
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An alternative is to alter your `$PATH` to include the directory where `new.py` is located. E.g., if `new.py` is in `$HOME/work/playful_python/bin/`, then add this directory to your `$PATH` -- probably by editing `.bashrc` or `.bash_profile` located in your `$HOME` directory (if you use `bash`). See the documentation for your shell of choice to understand how to edit and persist your `$PATH`.
47+
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For what it's worth, I always create a `$HOME/.local` directory for local installations of software I need, so I add `$HOME/.local/bin` to my `$PATH`. Then I copy programs like `new.py` there and they are available to me anywhere on the system.
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## Testing your programs
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# Chapter 4: Howler
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Write a Python program `howler.py` that will uppercase all the text from the command line or from a file.
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Write a Python program `howler.py` that will uppercase all the text from the command line or from a file. The program should also take a named option of `-o|--outfile` to write the output. The default output should be *standard out* (STDOUT).
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````
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$ ./howler.py
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ONE WORD: PLASTICS!
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$ ./howler.py ../inputs/fox.txt
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THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.
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$ ./howler.py -o out.txt ../inputs/fox.txt
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$ cat out.txt
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THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.
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````
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\newpage
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## Solution
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text = text.rstrip()
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````
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On line 39, we decide where to put the output of our program. The `if` expression will open `out_file` for writing text if `out_file` has been defined. The default value for `out_file` is the empty string which is effectively `False` when evaluated in a Boolean content. Unless the user provides a value, the output file handle `out_fh` will be `sys.stdout`. T
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On line 39, we decide where to put the output of our program. The `if` expression will open `out_file` for writing text if `out_file` has been defined. The default value for `out_file` is the empty string which is effectively `False` when evaluated in a Boolean content. Unless the user provides a value, the output file handle `out_fh` will be `sys.stdout`.
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To get uppercase, we can use the `text.upper` method. You can either `out_fh.write` this new text or use `print(..., file=...)`, noting which needs a newline and which does not. You can use `fh.close()` to close the file handle, but it's not entirely necessary as the program immediately ends after this. Still, it's good practice to close your file handles.
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\newpage
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# Chapter 5: Apples and Bananas
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‎coin_combos/README.md‎

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‎coin_combos/solution.py‎

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‎first_bank_of_change/README.md‎

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# First Bank of Change
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Write a Python program that will figure out all the different combinations of pennies, nickels, dimes, and quarters in a given `value` provided as a single positional argument. The value must be greater than 0 and less than or equal to 100.
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Write a Python program called `fboc.py` that will figure out all the different combinations of pennies, nickels, dimes, and quarters in a given `value` provided as a single positional argument. The value must be greater than 0 and less than or equal to 100.
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````
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$ ./combos.py
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usage: combos.py [-h] int
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combos.py: error: the following arguments are required: int
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$ ./combos.py -h
10-
usage: combos.py [-h] int
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$ ./fboc.py
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usage: fboc.py [-h] int
8+
fboc.py: error: the following arguments are required: int
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$ ./fboc.py -h
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usage: fboc.py [-h] int
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Coin combos for value
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First Bank of Change
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positional arguments:
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int Sum
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optional arguments:
1818
-h, --help show this help message and exit
19-
$ ./combos.py 1
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$ ./fboc.py 0
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usage: fboc.py [-h] int
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fboc.py: error: value "0" must be > 0 and <= 100
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$ ./fboc.py 124
23+
usage: fboc.py [-h] int
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fboc.py: error: value "124" must be > 0 and <= 100
25+
$ ./fboc.py 1
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If you give me 1 cent, I can give you:
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1: 1 penny
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$ ./combos.py 4
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$ ./fboc.py 4
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If you give me 4 cents, I can give you:
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1: 4 pennies
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$ ./combos.py 6
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$ ./fboc.py 6
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If you give me 6 cents, I can give you:
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1: 6 pennies
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2: 1 nickel, 1 penny
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$ ./combos.py 13
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$ ./fboc.py 13
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If you give me 13 cents, I can give you:
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1: 13 pennies
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2: 1 dime, 3 pennies
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3: 1 nickel, 8 pennies
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4: 2 nickels, 3 pennies
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$ ./combos.py 27
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$ ./fboc.py 27
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If you give me 27 cents, I can give you:
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1: 27 pennies
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2: 1 quarter, 2 pennies
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‎first_bank_of_change/solution.py‎

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"""Get command-line arguments"""
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parser = argparse.ArgumentParser(
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description='Coin combos for value',
14+
description='First Bank of Change',
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formatter_class=argparse.ArgumentDefaultsHelpFormatter)
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parser.add_argument('value', metavar='int', type=int, help='Sum')
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args = parser.parse_args()
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if not 0 < args.value <= 100:
22-
parser.error('value "{}" must be > 1 and <= 100'.format(args.value))
22+
parser.error('value "{}" must be > 0 and <= 100'.format(args.value))
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return args
2525

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‎hamming_chain/.log‎

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