Why do hyphens in module names generate syntax error?

Question

I'm using python 2.6 and get the following when importing a module:

  File "./test-nmea-uploader.py", line 11
    import nmea-uploader as sut
               ^
SyntaxError: invalid syntax

Why is that so? The python style guide seems to hold no mention about using hyphens in names, although it suggest the use of underscores.

Alan

Answer 1

According to http://docs.python.org/reference/lexical_analysis.html#identifiers, any identifier must start with a lowercase/uppercase letter or an underscore and contain lowercase/uppercase letters, numbers or an underscore.

Package names are identifiers, so they are bound to the same rules.

In addition, nmea-uploader might also mean the subtraction of uploader from nmea. Since you can import a package anywhere in a python file, if you have defined the variables nmea and uploader in advance, the interpreter would get confused if a hyphen was allowed for identifier names.