cpython/Doc/c-api/veryhigh.rst

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.. highlightlang:: c
.. _veryhigh:
*************************
The Very High Level Layer
*************************
The functions in this chapter will let you execute Python source code given in a
file or a buffer, but they will not let you interact in a more detailed way with
the interpreter.
Several of these functions accept a start symbol from the grammar as a
parameter. The available start symbols are :const:`Py_eval_input`,
:const:`Py_file_input`, and :const:`Py_single_input`. These are described
following the functions which accept them as parameters.
Note also that several of these functions take :ctype:`FILE\*` parameters. One
particular issue which needs to be handled carefully is that the :ctype:`FILE`
structure for different C libraries can be different and incompatible. Under
Windows (at least), it is possible for dynamically linked extensions to actually
use different libraries, so care should be taken that :ctype:`FILE\*` parameters
are only passed to these functions if it is certain that they were created by
the same library that the Python runtime is using.
.. cfunction:: int Py_Main(int argc, char **argv)
The main program for the standard interpreter. This is made available for
programs which embed Python. The *argc* and *argv* parameters should be
prepared exactly as those which are passed to a C program's :cfunc:`main`
function. It is important to note that the argument list may be modified (but
the contents of the strings pointed to by the argument list are not). The return
value will be ```0``` if the interpreter exits normally (ie, without an
exception), ``1`` if the interpreter exits due to an exception, or ``2``
if the parameter list does not represent a valid Python command line.
Note that if an otherwise unhandled :exc:`SystemExit` is raised, this
function will not return ``1``, but exit the process, as long as
``Py_InspectFlag`` is not set.
.. cfunction:: int PyRun_AnyFile(FILE *fp, const char *filename)
This is a simplified interface to :cfunc:`PyRun_AnyFileExFlags` below, leaving
*closeit* set to ``0`` and *flags* set to *NULL*.
.. cfunction:: int PyRun_AnyFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)
This is a simplified interface to :cfunc:`PyRun_AnyFileExFlags` below, leaving
the *closeit* argument set to ``0``.
.. cfunction:: int PyRun_AnyFileEx(FILE *fp, const char *filename, int closeit)
This is a simplified interface to :cfunc:`PyRun_AnyFileExFlags` below, leaving
the *flags* argument set to *NULL*.
.. cfunction:: int PyRun_AnyFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)
If *fp* refers to a file associated with an interactive device (console or
terminal input or Unix pseudo-terminal), return the value of
:cfunc:`PyRun_InteractiveLoop`, otherwise return the result of
:cfunc:`PyRun_SimpleFile`. If *filename* is *NULL*, this function uses
``"???"`` as the filename.
.. cfunction:: int PyRun_SimpleString(const char *command)
This is a simplified interface to :cfunc:`PyRun_SimpleStringFlags` below,
leaving the *PyCompilerFlags\** argument set to NULL.
.. cfunction:: int PyRun_SimpleStringFlags(const char *command, PyCompilerFlags *flags)
Executes the Python source code from *command* in the :mod:`__main__` module
according to the *flags* argument. If :mod:`__main__` does not already exist, it
is created. Returns ``0`` on success or ``-1`` if an exception was raised. If
there was an error, there is no way to get the exception information. For the
meaning of *flags*, see below.
Note that if an otherwise unhandled :exc:`SystemExit` is raised, this
function will not return ``-1``, but exit the process, as long as
``Py_InspectFlag`` is not set.
.. cfunction:: int PyRun_SimpleFile(FILE *fp, const char *filename)
This is a simplified interface to :cfunc:`PyRun_SimpleFileExFlags` below,
leaving *closeit* set to ``0`` and *flags* set to *NULL*.
.. cfunction:: int PyRun_SimpleFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)
This is a simplified interface to :cfunc:`PyRun_SimpleFileExFlags` below,
leaving *closeit* set to ``0``.
.. cfunction:: int PyRun_SimpleFileEx(FILE *fp, const char *filename, int closeit)
This is a simplified interface to :cfunc:`PyRun_SimpleFileExFlags` below,
leaving *flags* set to *NULL*.
.. cfunction:: int PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)
Similar to :cfunc:`PyRun_SimpleStringFlags`, but the Python source code is read
from *fp* instead of an in-memory string. *filename* should be the name of the
file. If *closeit* is true, the file is closed before PyRun_SimpleFileExFlags
returns.
.. cfunction:: int PyRun_InteractiveOne(FILE *fp, const char *filename)
This is a simplified interface to :cfunc:`PyRun_InteractiveOneFlags` below,
leaving *flags* set to *NULL*.
.. cfunction:: int PyRun_InteractiveOneFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)
Read and execute a single statement from a file associated with an
interactive device according to the *flags* argument. The user will be
prompted using ``sys.ps1`` and ``sys.ps2``. Returns ``0`` when the input was
executed successfully, ``-1`` if there was an exception, or an error code
from the :file:`errcode.h` include file distributed as part of Python if
there was a parse error. (Note that :file:`errcode.h` is not included by
:file:`Python.h`, so must be included specifically if needed.)
.. cfunction:: int PyRun_InteractiveLoop(FILE *fp, const char *filename)
This is a simplified interface to :cfunc:`PyRun_InteractiveLoopFlags` below,
leaving *flags* set to *NULL*.
.. cfunction:: int PyRun_InteractiveLoopFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)
Read and execute statements from a file associated with an interactive device
until EOF is reached. The user will be prompted using ``sys.ps1`` and
``sys.ps2``. Returns ``0`` at EOF.
.. cfunction:: struct _node* PyParser_SimpleParseString(const char *str, int start)
This is a simplified interface to
:cfunc:`PyParser_SimpleParseStringFlagsFilename` below, leaving *filename* set
to *NULL* and *flags* set to ``0``.
.. cfunction:: struct _node* PyParser_SimpleParseStringFlags( const char *str, int start, int flags)
This is a simplified interface to
:cfunc:`PyParser_SimpleParseStringFlagsFilename` below, leaving *filename* set
to *NULL*.
.. cfunction:: struct _node* PyParser_SimpleParseStringFlagsFilename( const char *str, const char *filename, int start, int flags)
Parse Python source code from *str* using the start token *start* according to
the *flags* argument. The result can be used to create a code object which can
be evaluated efficiently. This is useful if a code fragment must be evaluated
many times.
.. cfunction:: struct _node* PyParser_SimpleParseFile(FILE *fp, const char *filename, int start)
This is a simplified interface to :cfunc:`PyParser_SimpleParseFileFlags` below,
leaving *flags* set to ``0``
.. cfunction:: struct _node* PyParser_SimpleParseFileFlags(FILE *fp, const char *filename, int start, int flags)
Similar to :cfunc:`PyParser_SimpleParseStringFlagsFilename`, but the Python
source code is read from *fp* instead of an in-memory string.
.. cfunction:: PyObject* PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
This is a simplified interface to :cfunc:`PyRun_StringFlags` below, leaving
*flags* set to *NULL*.
.. cfunction:: PyObject* PyRun_StringFlags(const char *str, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
Execute Python source code from *str* in the context specified by the
dictionaries *globals* and *locals* with the compiler flags specified by
*flags*. The parameter *start* specifies the start token that should be used to
parse the source code.
Returns the result of executing the code as a Python object, or *NULL* if an
exception was raised.
.. cfunction:: PyObject* PyRun_File(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals)
This is a simplified interface to :cfunc:`PyRun_FileExFlags` below, leaving
*closeit* set to ``0`` and *flags* set to *NULL*.
.. cfunction:: PyObject* PyRun_FileEx(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit)
This is a simplified interface to :cfunc:`PyRun_FileExFlags` below, leaving
*flags* set to *NULL*.
.. cfunction:: PyObject* PyRun_FileFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
This is a simplified interface to :cfunc:`PyRun_FileExFlags` below, leaving
*closeit* set to ``0``.
.. cfunction:: PyObject* PyRun_FileExFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit, PyCompilerFlags *flags)
Similar to :cfunc:`PyRun_StringFlags`, but the Python source code is read from
*fp* instead of an in-memory string. *filename* should be the name of the file.
If *closeit* is true, the file is closed before :cfunc:`PyRun_FileExFlags`
returns.
.. cfunction:: PyObject* Py_CompileString(const char *str, const char *filename, int start)
This is a simplified interface to :cfunc:`Py_CompileStringFlags` below, leaving
*flags* set to *NULL*.
.. cfunction:: PyObject* Py_CompileStringFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags)
Parse and compile the Python source code in *str*, returning the resulting code
object. The start token is given by *start*; this can be used to constrain the
code which can be compiled and should be :const:`Py_eval_input`,
:const:`Py_file_input`, or :const:`Py_single_input`. The filename specified by
*filename* is used to construct the code object and may appear in tracebacks or
:exc:`SyntaxError` exception messages. This returns *NULL* if the code cannot
be parsed or compiled.
.. cfunction:: PyObject* PyEval_EvalCode(PyCodeObject *co, PyObject *globals, PyObject *locals)
This is a simplified interface to :cfunc:`PyEval_EvalCodeEx`, with just
the code object, and the dictionaries of global and local variables.
The other arguments are set to *NULL*.
.. cfunction:: PyObject* PyEval_EvalCodeEx(PyCodeObject *co, PyObject *globals, PyObject *locals, PyObject **args, int argcount, PyObject **kws, int kwcount, PyObject **defs, int defcount, PyObject *closure)
Evaluate a precompiled code object, given a particular environment for its
evaluation. This environment consists of dictionaries of global and local
variables, arrays of arguments, keywords and defaults, and a closure tuple of
cells.
.. cfunction:: PyObject* PyEval_EvalFrame(PyFrameObject *f)
Evaluate an execution frame. This is a simplified interface to
PyEval_EvalFrameEx, for backward compatibility.
.. cfunction:: PyObject* PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
This is the main, unvarnished function of Python interpretation. It is
literally 2000 lines long. The code object associated with the execution
frame *f* is executed, interpreting bytecode and executing calls as needed.
The additional *throwflag* parameter can mostly be ignored - if true, then
it causes an exception to immediately be thrown; this is used for the
:meth:`throw` methods of generator objects.
.. cfunction:: int PyEval_MergeCompilerFlags(PyCompilerFlags *cf)
This function changes the flags of the current evaluation frame, and returns
true on success, false on failure.
.. cvar:: int Py_eval_input
.. index:: single: Py_CompileString()
The start symbol from the Python grammar for isolated expressions; for use with
:cfunc:`Py_CompileString`.
.. cvar:: int Py_file_input
.. index:: single: Py_CompileString()
The start symbol from the Python grammar for sequences of statements as read
from a file or other source; for use with :cfunc:`Py_CompileString`. This is
the symbol to use when compiling arbitrarily long Python source code.
.. cvar:: int Py_single_input
.. index:: single: Py_CompileString()
The start symbol from the Python grammar for a single statement; for use with
:cfunc:`Py_CompileString`. This is the symbol used for the interactive
interpreter loop.
.. ctype:: struct PyCompilerFlags
This is the structure used to hold compiler flags. In cases where code is only
being compiled, it is passed as ``int flags``, and in cases where code is being
executed, it is passed as ``PyCompilerFlags *flags``. In this case, ``from
__future__ import`` can modify *flags*.
Whenever ``PyCompilerFlags *flags`` is *NULL*, :attr:`cf_flags` is treated as
equal to ``0``, and any modification due to ``from __future__ import`` is
discarded. ::
struct PyCompilerFlags {
int cf_flags;
}
.. cvar:: int CO_FUTURE_DIVISION
This bit can be set in *flags* to cause division operator ``/`` to be
interpreted as "true division" according to :pep:`238`.