A Good First Program Python

A Good First Program Python

Remember, you should have spent a good amount of time in Exercise 0, learning how to install a text editor, run the text editor, run the Terminal, and work with both of them. If you haven’t done that, then do not go on. You will not have a good time. This is the only time I’ll start an exercise with a warning that you should not skip or get ahead of yourself.

print "Hello World!"
print "Hello Again"
print "I like typing this."
print "This is fun."
print 'Yay! Printing.'
print "I'd much rather you 'not'."
print 'I "said" do not touch this.'
  1. Notice I did not type the line numbers on the left. Those are printed in the book so I can talk about specifi c lines by saying, “See line 5 . . .” You do not type those into Python scripts.
  2. Notice I have the print at the beginning of the line and how it looks exactly the same as what I have above. Exactly means exactly, not kind of sort of the same. Every single character has to match for it to work. But the colors are all different. Color doesn’t matter; only the characters you type.

Then in Terminal, run the fi le by typing:

python ex1.py

If you did it right, then you should see the same output I have below. If not, you have done something wrong. No, the computer is not wrong.

Study Drills

Each exercise also contains Study Drills. The Study Drills contain things you should try to do. If you can’t, skip it and come back later.

  1. Make your script print another line.
  2. Make your script print only one of the lines.
  3. Put a “#” (octothorpe) character at the beginning of a line. What did it do? Try to fi nd out what this character does

Common Student Questions

Can I use IDLE?

No, you should use Terminal on OSX and PowerShell on Windows, just like I have here. If you don’t know how to use those, then you can go read the Command Line Crash Course in the appendix.

How do you get colors in your editor?

Save your fi le fi rst as a .py fi le, such as ex1.py. Then you’ll have color when you type.

I get SyntaxError: invalid syntax when I run ex1.py.

You are probably trying to run Python, then trying to type Python again. Close your Terminal, start it again, and right away type only python ex1.py.

I get can’t open file ‘ex1.py’: [Errno 2] No such file or directory.

You need to be in the same directory as the fi le you created. Make sure you use the cd command to go there fi rst. For example, if you saved your fi le in lpthw/ex1.py, then you would do cd lpthw/ before trying to run python ex1.py. If you don’t know what any of that means, then go through the Command Line Crash Course (CLI- CC) mentioned in the fi rst question.

My fi le doesn’t run; I just get the prompt back with no output.

You most likely took the previous code literally and thought that print “Hello World!” meant to literally print just “Hello World!” into the fi le, without the print. Your fi le has to be exactly like mine in the previous code and all the screenshots; I have print “Hello World!” and print before every line. Make sure your code is like mine and it should work.