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Utilities to compile possibly incomplete Python source code.
This module provides two interfaces, broadly similar to the builtin
function compile(), which take program text, a filename and a 'mode'
and:
- Return code object if the command is complete and valid
- Return None if the command is incomplete
- Raise SyntaxError, ValueError or OverflowError if the command is a
syntax error (OverflowError and ValueError can be produced by
malformed literals).
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 2.2, 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.
The two interfaces are:
compile_command(source, filename, symbol):
Compiles a single command in the manner described above.
CommandCompiler():
Instances of this class have __call__ methods identical in
signature to compile_command; the difference is that if the
instance compiles program text containing a __future__ statement,
the instance 'remembers' and compiles all subsequent program texts
with the statement in force.
The module also provides another class:
Compile():
Instances of this class act like the built-in function compile,
but with 'memory' in the sense described above.
Instances of this class have __call__ methods identical in
signature to compile_command; the difference is that if the
instance compiles program text containing a __future__ statement,
the instance 'remembers' and compiles all subsequent program texts
with the statement in force.
Instances of this class behave much like the built-in compile
function, but if one is used to compile text containing a future
statement, it "remembers" and compiles all subsequent program texts
with the statement in force.
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), "exec"
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, ValueError or OverflowError if the command is a
syntax error (OverflowError and ValueError can be produced by
malformed literals).
PyCF_DONT_IMPLY_DEDENT = 512