| | |
- compile_command(source, filename='<input>', symbol='single')
- Compile a command and determine whether it is incomplete.
- Arguments:
- source -- the source string; may contain \n characters
- filename -- optional filename from which source was read; default "<input>"
- symbol -- optional grammar start symbol; "single" (default) or "eval"
- Return value / exceptions raised:
- - Return a code object if the command is complete and valid
- - Return None if the command is incomplete
- - Raise SyntaxError or OverflowError if the command is a syntax error
- (OverflowError if the error is in a numeric constant)
- Approach:
- First, check if the source consists entirely of blank lines and
- comments; if so, replace it with 'pass', because the built-in
- parser doesn't always do the right thing for these.
- Compile three times: as is, with \n, and with \n\n appended. If
- it compiles as is, it's complete. If it compiles with one \n
- appended, we expect more. If it doesn't compile either way, we
- compare the error we get when compiling with \n or \n\n appended.
- If the errors are the same, the code is broken. But if the errors
- are different, we expect more. Not intuitive; not even guaranteed
- to hold in future releases; but this matches the compiler's
- behavior from Python 1.4 through 1.5.2, at least.
- Caveat:
- It is possible (but not likely) that the parser stops parsing
- with a successful outcome before reaching the end of the source;
- in this case, trailing symbols may be ignored instead of causing an
- error. For example, a backslash followed by two newlines may be
- followed by arbitrary garbage. This will be fixed once the API
- for the parser is better.
|