Check the name of the file that your code tries to import. If it is
supposed to be one of the standard Python libraries, you probably made a
spelling mistake in the name. Either that, or you added .py to the
name – you should not do that. If the error concerns pcinput or
pcmaze, then probably you either did not build these files (check
Appendix
311
or
322
to solve the problem), or you placed them in a location that Python has
no access to. In the last case, make sure you copy them to the same
place as where you keep your Python programs.
You try to open a file that Python cannot find. You might have forgotten to include the complete pathname in the file name, or you think the file is located in the current directory while actually it is not. Or maybe your code tries to use one of the standard test files that I use for the book, and you do not have those yet. If that is the case, check Appendix 333 to learn how to make them.
When one or more syntax errors are reported, you should try to solve the
one reported first. Further errors are often caused by the first one.
The line of code where Python discovered the error is reported with the
error. Check that line. Also check the line above it: it might very well
happen that you made an error in a line of code, but Python only notices
it when it processes the next line. Syntax highlighting may also give an
indication of where you made your mistake. Common syntax errors that
beginning programmers make are forgetting to include a colon (:) at
the end of an if, while, or for statement, misspelling the name of
variables that they created, or making errors in indentation.
You have used a character in your program that Python cannot process. For instance, you might have placed your own name in the code (maybe even only in a comment), and your name is spelled with a special character that is not directly found on the keyboard. Stick to characters that are found on the US keyboard. It is not that you cannot include special characters in your code, but the rules for doing that are explained in later chapters in this book.
Make sure that you use Python version 3.4 or later. The code was written with Python 3.4, and I have noticed that some code elements do not work correctly with earlier versions of Python.
Maybe you built an endless loop in your program, so the program is
actually working but never getting to the point where it produces
output. Check your loops. Sometimes it is helpful to include a print()
statement at the start of your program, just to see that the program
actually has started. print() statements in the code might also help
to discover where it gets stuck.
Make sure that you spelled your call to the function (or class) correctly. Remember that Python is case sensitive! If the spelling seems to be correct, make sure that you have not created a variable with the same name as the function (or class). If you did, this will definitely destroy the possibilities of Python to access your function (or class).
Sometimes it is good to take a break. Put the program away, go home, play some games, exercise, take a shower, anything. Get back to it tomorrow. Ask any programmer: sometimes you get stuck and cannot resolve a problem, for which the solution is immediately clear to you when you come in the next day. What might also help is get someone else in and explain your problem to them. Often, during such an explanation, you suddenly see what you were doing wrong all this time. What you definitely should not do, however, is continue writing your program without resolving the problem. You will only create a bigger mess. A much better idea would be to make a copy of your program and then actually remove/simplify code until the program starts working. That at least gives you an indication where you have to look for the error.