.. highlight:: 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 :c:expr:`FILE*` parameters. One
particular issue which needs to be handled carefully is that the :c:expr:`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 :c:expr:`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.
.. c:function:: int Py_Main(int argc, wchar_t **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 :c:func:`main`
function (converted to wchar_t according to the user's locale). 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 (i.e., 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.
.. c:function:: int Py_BytesMain(int argc, char **argv)
Similar to :c:func:`Py_Main` but *argv* is an array of bytes strings.
.. versionadded:: 3.8
.. c:function:: int PyRun_AnyFile(FILE *fp, const char *filename)
This is a simplified interface to :c:func:`PyRun_AnyFileExFlags` below, leaving
*closeit* set to ``0`` and *flags* set to ``NULL``.
.. c:function:: int PyRun_AnyFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)
This is a simplified interface to :c:func:`PyRun_AnyFileExFlags` below, leaving
the *closeit* argument set to ``0``.
.. c:function:: int PyRun_AnyFileEx(FILE *fp, const char *filename, int closeit)
This is a simplified interface to :c:func:`PyRun_AnyFileExFlags` below, leaving
the *flags* argument set to ``NULL``.
.. c:function:: 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
:c:func:`PyRun_InteractiveLoop`, otherwise return the result of
:c:func:`PyRun_SimpleFile`. *filename* is decoded from the filesystem
encoding (:func:`sys.getfilesystemencoding`). If *filename* is ``NULL``, this
function uses ``"???"`` as the filename.
If *closeit* is true, the file is closed before
``PyRun_SimpleFileExFlags()`` returns.
.. c:function:: int PyRun_SimpleString(const char *command)
This is a simplified interface to :c:func:`PyRun_SimpleStringFlags` below,
leaving the :c:struct:`PyCompilerFlags`\* argument set to ``NULL``.
.. c:function:: 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.
.. c:function:: int PyRun_SimpleFile(FILE *fp, const char *filename)
This is a simplified interface to :c:func:`PyRun_SimpleFileExFlags` below,
leaving *closeit* set to ``0`` and *flags* set to ``NULL``.
.. c:function:: int PyRun_SimpleFileEx(FILE *fp, const char *filename, int closeit)
This is a simplified interface to :c:func:`PyRun_SimpleFileExFlags` below,
leaving *flags* set to ``NULL``.
.. c:function:: int PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)
Similar to :c:func:`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, it is decoded from :term:`filesystem encoding and error handler`.
If *closeit* is true, the file is closed before
``PyRun_SimpleFileExFlags()`` returns.
.. note::
On Windows, *fp* should be opened as binary mode (e.g. ``fopen(filename, "rb")``).
Otherwise, Python may not handle script file with LF line ending correctly.
.. c:function:: int PyRun_InteractiveOne(FILE *fp, const char *filename)
This is a simplified interface to :c:func:`PyRun_InteractiveOneFlags` below,
leaving *flags* set to ``NULL``.
.. c:function:: 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``. *filename* is decoded from the
:term:`filesystem encoding and error handler`.
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.)
.. c:function:: int PyRun_InteractiveLoop(FILE *fp, const char *filename)
This is a simplified interface to :c:func:`PyRun_InteractiveLoopFlags` below,
leaving *flags* set to ``NULL``.
.. c:function:: 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``. *filename* is decoded from the :term:`filesystem encoding and
error handler`. Returns ``0`` at EOF or a negative number upon failure.
.. c:var:: int (*PyOS_InputHook)(void)
Can be set to point to a function with the prototype
``int func(void)``. The function will be called when Python's
interpreter prompt is about to become idle and wait for user input
from the terminal. The return value is ignored. Overriding this
hook can be used to integrate the interpreter's prompt with other
event loops, as done in the :file:`Modules/_tkinter.c` in the
Python source code.
.. c:var:: char* (*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, const char *)
Can be set to point to a function with the prototype
``char *func(FILE *stdin, FILE *stdout, char *prompt)``,
overriding the default function used to read a single line of input
at the interpreter's prompt. The function is expected to output
the string *prompt* if it's not ``NULL``, and then read a line of
input from the provided standard input file, returning the
resulting string. For example, The :mod:`readline` module sets
this hook to provide line-editing and tab-completion features.
The result must be a string allocated by :c:func:`PyMem_RawMalloc` or
:c:func:`PyMem_RawRealloc`, or ``NULL`` if an error occurred.
.. versionchanged:: 3.4
The result must be allocated by :c:func:`PyMem_RawMalloc` or
:c:func:`PyMem_RawRealloc`, instead of being allocated by
:c:func:`PyMem_Malloc` or :c:func:`PyMem_Realloc`.
.. c:function:: PyObject* PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
This is a simplified interface to :c:func:`PyRun_StringFlags` below, leaving
*flags* set to ``NULL``.
.. c:function:: 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
objects *globals* and *locals* with the compiler flags specified by
*flags*. *globals* must be a dictionary; *locals* can be any object
that implements the mapping protocol. 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.
.. c:function:: PyObject* PyRun_File(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals)
This is a simplified interface to :c:func:`PyRun_FileExFlags` below, leaving
*closeit* set to ``0`` and *flags* set to ``NULL``.
.. c:function:: PyObject* PyRun_FileEx(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit)
This is a simplified interface to :c:func:`PyRun_FileExFlags` below, leaving
*flags* set to ``NULL``.
.. c:function:: PyObject* PyRun_FileFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
This is a simplified interface to :c:func:`PyRun_FileExFlags` below, leaving
*closeit* set to ``0``.
.. c:function:: PyObject* PyRun_FileExFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit, PyCompilerFlags *flags)
Similar to :c:func:`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,
it is decoded from the :term:`filesystem encoding and error handler`.
If *closeit* is true, the file is closed before :c:func:`PyRun_FileExFlags`
returns.
.. c:function:: PyObject* Py_CompileString(const char *str, const char *filename, int start)
This is a simplified interface to :c:func:`Py_CompileStringFlags` below, leaving
*flags* set to ``NULL``.
.. c:function:: PyObject* Py_CompileStringFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags)
This is a simplified interface to :c:func:`Py_CompileStringExFlags` below, with
*optimize* set to ``-1``.
.. c:function:: PyObject* Py_CompileStringObject(const char *str, PyObject *filename, int start, PyCompilerFlags *flags, int optimize)
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.
The integer *optimize* specifies the optimization level of the compiler; a
value of ``-1`` selects the optimization level of the interpreter as given by
:option:`-O` options. Explicit levels are ``0`` (no optimization;
``__debug__`` is true), ``1`` (asserts are removed, ``__debug__`` is false)
or ``2`` (docstrings are removed too).
.. versionadded:: 3.4
.. c:function:: PyObject* Py_CompileStringExFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags, int optimize)
Like :c:func:`Py_CompileStringObject`, but *filename* is a byte string
decoded from the :term:`filesystem encoding and error handler`.
.. versionadded:: 3.2
.. c:function:: PyObject* PyEval_EvalCode(PyObject *co, PyObject *globals, PyObject *locals)
This is a simplified interface to :c:func:`PyEval_EvalCodeEx`, with just
the code object, and global and local variables. The other arguments are
set to ``NULL``.
.. c:function:: PyObject* PyEval_EvalCodeEx(PyObject *co, PyObject *globals, PyObject *locals, PyObject *const *args, int argcount, PyObject *const *kws, int kwcount, PyObject *const *defs, int defcount, PyObject *kwdefs, PyObject *closure)
Evaluate a precompiled code object, given a particular environment for its
evaluation. This environment consists of a dictionary of global variables,
a mapping object of local variables, arrays of arguments, keywords and
defaults, a dictionary of default values for :ref:`keyword-only
<keyword-only_parameter>` arguments and a closure tuple of cells.
.. c:function:: PyObject* PyEval_EvalFrame(PyFrameObject *f)
Evaluate an execution frame. This is a simplified interface to
:c:func:`PyEval_EvalFrameEx`, for backward compatibility.
.. c:function:: PyObject* PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
This is the main, unvarnished function of Python interpretation. 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:`~generator.throw`
methods of generator objects.
.. versionchanged:: 3.4
This function now includes a debug assertion to help ensure that it
does not silently discard an active exception.
.. c:function:: int PyEval_MergeCompilerFlags(PyCompilerFlags *cf)
This function changes the flags of the current evaluation frame, and returns
true on success, false on failure.
.. c:var:: int Py_eval_input
.. index:: single: Py_CompileString()
The start symbol from the Python grammar for isolated expressions; for use with
:c:func:`Py_CompileString`.
.. c:var:: 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 :c:func:`Py_CompileString`. This is
the symbol to use when compiling arbitrarily long Python source code.
.. c:var:: int Py_single_input
.. index:: single: Py_CompileString()
The start symbol from the Python grammar for a single statement; for use with
:c:func:`Py_CompileString`. This is the symbol used for the interactive
interpreter loop.
.. c: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.
.. c:member:: int cf_flags
Compiler flags.
.. c:member:: int cf_feature_version
*cf_feature_version* is the minor Python version. It should be
initialized to ``PY_MINOR_VERSION``.
The field is ignored by default, it is used if and only if
``PyCF_ONLY_AST`` flag is set in *cf_flags*.
.. versionchanged:: 3.8
Added *cf_feature_version* field.
.. c:var:: 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`.
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