Learn python the hard way download update version

In fact, there are a lot of chapters that have a blank page between it and the next chapter, so there is some filler going on here. Each chapter also has some drills and some common student questions in them. From simple things like strings, dictionaries, and lists, to conditionals, loops, functions, and classes. They are all covered here. In the introduction, Mr. Shaw makes a big deal about how if you, the reader, feel like he is insulting your intelligence, then you are not in the intended audience for this book.

I assume he is attempting to be funny, but he comes across as snarky, at best. It is mostly so you can then find out what a floating point number is and ask this question. See the Study Drills. A string is how you make something that your program might give to a human. You print strings, save strings to files, send strings to web servers, and many other things. Strings are really handy, so in this exercise you will learn how to make strings that have variables em- bedded in them.

Put these variables in there. He's 74 inches tall. He's pounds heavy. Actually that's not too heavy. He's got Blue eyes and Brown hair. His teeth are usually White depending on the coffee. If I add 35, 74, and I get Study Drills 1. Try to write some variables that convert the inches and pounds to centimeters and kilograms.

Do not just type in the measurements. Work out the math in Python. No, 1 is not a valid variable name. They need to start with a character, so a1 would work, but 1 will not. How can I round a floating point number? You can use the round function like this: round 1. Why does this not make sense to me? Try making the numbers in this script your measurements. Keep going and more exercises will explain it more. In this exercise we create a bunch of variables with complex strings so you can see what they are for.

First an explanation of strings. Python knows you want something to be a string when you put either " double-quotes or ' single-quotes around the text.

You saw this many times with your use of print when you put the text you want to go inside the string inside " or ' after the print to print the string. Strings can contain any number of variables that are in your Python script. We will now type in a whole bunch of strings, variables, and formats, and print them. You will also practice using short abbreviated variable names. Those who know binary and those who don't. I said: There are 10 types of people.

I also said: 'Those who know binary and those who don't. False This is the left side of Go through this program and write a comment above each line explaining it.

Find all the places where a string is put inside a string. There are four places. Are you sure there are only four places? How do you know? Maybe I like lying. Break It You are now at a point where you can try to break your code to see what happens. Think of this as a game to devise the most clever way to break the code.

You can also find the simplest way to break it. Once you break the code, you then need to fix it. Give your friend your ex6. Then you try to find their error and fix it. Have fun with this, and remember that if you wrote this code once you can do it again.

If you take your damage too far, you can always type it in again for extra practice. The purpose is to build up your chops. See you in a few exercises, and do not skip! Do not paste! Its fleece was white as snow. And everywhere that Mary went. Go back through and write a comment on what each line does. Read each one backward or out loud to find your errors. From now on, when you make mistakes, write down on a piece of paper what kind of mistake you made.

When you go to the next exercise, look at the mistakes you have made and try not to make them in this new one. Remember that everyone makes mistakes. They make mistakes all the time. Break It Did you have fun breaking the code in Exercise 6? Your goal is to find as many different ways to break your code until you get tired or exhaust all possibilities. Is it normal to write an English comment for every line of code like you say to do in Study Drill 1?

No, you write comments only to explain difficult to understand code or why you did something. Why is usually much more important, and then you try to write the code so that it explains how some- thing is being done on its own.

However, sometimes you have to write such nasty code to solve a problem that it does need a comment on every line. When you see me write formatter.

Take the formatter string defined on line 1. Call its format function, which is similar to telling it to do a command line command named format. This is like passing arguments to the command line command format.

This is what print is now printing out. Do your checks, write down your mistakes, and try not to make the same mistakes on the next exercise. Python recognizes True and False as keywords representing the concept of true and false. No, you should learn to use the command line. It is essential to learning programming and is a good place to start if you want to learn about programming.

IDLE will fail for you when you get further in the book. I start with code that you might not understand, then more exercises explain the concept. With the three double-quotes. We'll be able to type as much as we like. Even 4 lines if we want, or 5, or 6. Check your work, write down your mistakes, try not to make them on the next exercise.

Are you breaking your code and then fixing it? You have to type them like """ and not " " ", meaning with no spaces between each one. What if I wanted to start the months on a new line? Most programming errors in the beginning and even later are simple spelling mistakes, typos, or getting simple things out of order.

In Exercise 9 I threw you some new stuff, just to keep you on your toes. I showed you two ways to make a string that goes across multiple lines.

These two characters put a new line character into the string at that point. An important escape sequence is to escape a single-quote ' or double-quote ". Imagine you have a string that uses double-quotes and you want to put a double-quote inside the string. If you write "I "understand" joe. To solve this problem you escape double-quotes and single-quotes so Python knows to include them in the string.

In this exercise the spacing is important to get right. You may not use many of these, but memorize their format and what they do anyway. Try them out in some strings to see if you can make them work. Escape What it does. Memorize all the escape sequences by putting them on flash cards. Use ''' triple-single-quote instead. Can you see why you might use that instead of """? Combine escape sequences and format strings to create a more complex format.

Should I continue? Yes, keep going. Sometimes, though, you may need to go back a few exercises and do them again. Think about why you would need this. They are different characters that do very different things. One concept I need you to understand is that each of these exercises can be combined to solve problems. Take what you know about format strings and write some new code that uses format strings and the escape sequences from this exercise.

Go with the ''' triple-single-quote style for now, but be ready to use either depending on what feels best or what everyone else is doing. You are doing a lot of printing to get you familiar with typing simple things, but those simple things are fairly boring. What we want to do now is get data into your programs. This is a little tricky because you have to learn to do two things that may not make sense right away, but trust me and do it anyway.

It will make sense in a few exercises. Most of what software does is the following: 1. Take some kind of input from a person. Change it. Print out something to show how it changed.

This tells print to not end the line with a newline character and go to the next line. Can you find other ways to use it? Try some of the samples you find. First thing is, go back and make the code exactly like mine. Next, run the script, and when it pauses, type your height in at your keyboard. For input you can also put in a prompt to show to a person so he knows what to type.

This is how you ask someone a question and get the answer. This means we can completely rewrite our previous exercise using just input to do all the prompting.

In Terminal, where you normally run python3. Read what it says. Get out of pydoc by typing q to quit. Look online for what the pydoc command does. Use pydoc to also read about open, file, os, and sys. Exit out of python3. Why does my pydoc not pause like yours does?

Sometimes if the help document is short enough to fit on one screen then pydoc will just print it. When I run pydoc I get more is not recognized as an internal. Some versions of Windows do not have that command, which means pydoc is broken for you.

You can skip this Study Drill and just search online for Python documentation when you need it. Try this, and then try to print out what you type. You know how you type python3. Well the ex Rather than give you all the features at once, Python asks you to say what you plan to use. This keeps your programs small, but it also acts as documentation for other programmers who read your code later.

This variable holds the arguments you pass to your Python script when you run it. In the exercises you will get to play with this more and see what happens.

Hold Up! I just used that name because I needed to trick you into learning what they are without jargon. Before you can continue, you need to learn their real name: modules. Pay attention! You have been running python scripts without command line arguments.

If you type only python3. Pay close attention to how I run it. This applies any time you see argv being used. Try giving fewer than three arguments to your script.

See that error you get? See if you can explain it. Write a script that has fewer arguments and one that has more. Make sure you give the unpacked variables good names. Combine input with argv to make a script that gets more input from a user.

Just use argv to get something, and input to get something else from the user. Remember that modules give you features. Remember that an important skill is paying attention to details.

If you look at the What You Should See section you see that I run the script with parameters on the command line. You should replicate how I ran it exactly. The difference has to do with where the user is re- quired to give input. If they give your script inputs on the command line, then you use argv. If you want them to input using the keyboard while the script is running, then use input.

Are the command line arguments strings? Yes, they come in as strings, even if you typed numbers on the command line. Use int to convert them just like with int input. How do you use the command line?

You should have learned to use it very quickly and fluently by now, but if you need to learn it at this stage, then read the Command Line Crash Course I wrote for this book in Appendix A. Just slap two lines at the end of this script that uses input to get something and then print it. From that, start playing with more ways to use both in the same script. You will need this for the next exercise where you learn to read and write files.

This is similar to a game like Zork or Adventure. Not sure where that is. Now if we want to make the prompt something else, we just change it in this one spot and rerun the script. Very handy. What You Should See When you run this, remember that you have to give the script your name for the argv arguments. I'd like to ask you a few questions. Do you like me zed? You live in San Francisco. And you have a Tandy computer. Find out what the games Zork and Adventure were.

Try to find a copy and play it. Change the prompt variable to something else entirely. Again, you have to run it right on the com- mand line, not inside Python. If you type python3. Close your window and then just type python3. Change that to have a different value. I get the error ValueError: need more than 1 value to unpack. Can I use double-quotes for the prompt variable?

You totally can. Go ahead and try that. You have a Tandy computer? I did when I was little. I get NameError: name 'prompt' is not defined when I run it. You either spelled the name of the prompt variable wrong or forgot that line. Go back and compare each line of code to mine, from at the bottom of the script to the top.

Any time you see this error, it means you spelled something wrong or forgot to create the variable. Now you will learn about reading from a file. Working with files is an easy way to erase your work if you are not careful. This exercise involves writing two files.

One is the usual ex Next we have line 5, where we use a new command open. Right now, run pydoc open and read the instructions. You just opened a file. Line 7 prints a little message, but on line 8 we have something very new and exciting. We call a function on txt named read. What you get back from open is a file, and it also has commands you can give it.

You give a file a command by using the. The difference is that txt. Do your read command with no parameters! I said pay attention! You have been running scripts with just the name of the script, but now that you are using argv you have to add arguments. Look at the very first line of the example below and you will see I do python ex If you do not type that you will get an error so pay attention!

It is really cool stuff. Lots and lots of fun to have in here. Study Drills This is a big jump, so be sure you do this Study Drill as best you can before moving on. Above each line, write out in English what that line does. If you are not sure, ask someone for help or search online.

Get rid of the lines where you use input and run the script again. Use only input and try the script that way. Why is one way of getting the filename better than another? Notice how you can open files and run read on them from within python3.

First thing, from the command line just type python3. Now you are in python3. Then you can type in code and Python will run it in little pieces. Play with that. To get out of it type quit and hit Enter. Why is there no error when we open the file twice? Python will not restrict you from opening a file more than once, and sometimes this is necessary.

What does from sys import argv mean? For now just understand that sys is a package, and this phrase just says to get the argv feature from that package. Make the code exactly like mine, then run it from the command line the exact same way I do. You can assign the result to a variable. Watch out if you care about the file.

In the early days of computers data was stored on each of these kinds of media, so many of the file operations still resemble a storage system that is linear. For now, these are the important commands you need to know. Some of them take parameters, but we do not really care about that. You only need to remember that write takes a parameter of a string you want to write to the file.

So go slow, do your checks, and make it run. One trick is to get bits of it running at a time. What You Should See There are actually two things you will see. Opening the file Truncating the file. Now I'm going to ask you for three lines. Now, open up the file you made in my case test. Neat, right? If you do not understand this, go back through and use the comment trick to get it squared away in your mind. One simple English comment above each line will help you understand or at least let you know what you need to research more.

Write a script similar to the last exercise that uses read and argv to read the file you just created. You must have seen many e-commerce websites selling this book. But you can download it free. All you need to do is,click here or the PDF Button below and book is in your device. Have a good python learning journey. Download PDF. Save my name, email, and website in this browser for the next time I comment. Next, re-run terminal window and type python in order to check installed version of the Python, type: python --version in order to exit python console type exit Pip Pip is a Python Package Manager.

Re-run terminal window Type pip , to check if package manager works You can type pip --version , in order to check version of the pip Installing Pip on Linux Open terminal Type sudo apt-get install python-pip Installing Pip on macOS Open terminal Type brew install python3 This command will install python and pip. Unit Testing UT in Python can be done with nose.

Install it via pip with the following command: sudo pip install nose UT can be also created with unittest package provided with Python.

Virtualenv virtualenv is a tool to create isolated Python environments. Scripts on Linux If we want to create a Python script for Linux, we should set the following header:!