.. highlightlang:: c

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:type:`FILE\*` parameters. One particular issue which needs to be handled carefully is that the :c:type:`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:type:`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 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.

.. c:function:: int PyRun_SimpleString(const char *command)

 This is a simplified interface to :c:func:`PyRun_SimpleStringFlags` below,
 leaving the *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 the filesystem encoding
 (:func:`sys.getfilesystemencoding`). 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
 filesystem encoding (:func:`sys.getfilesystemencoding`).

 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 filesystem encoding
 (:func:`sys.getfilesystemencoding`). 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:: struct _node* PyParser_SimpleParseString(const char *str, int start)

 This is a simplified interface to
 :c:func:`PyParser_SimpleParseStringFlagsFilename` below, leaving *filename* set
 to *NULL* and *flags* set to ``0``.

.. c:function:: struct _node* PyParser_SimpleParseStringFlags( const char *str, int start, int flags)

 This is a simplified interface to
 :c:func:`PyParser_SimpleParseStringFlagsFilename` below, leaving *filename* set
 to *NULL*.

.. c:function:: 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. *filename* is decoded from the filesystem encoding
 (:func:`sys.getfilesystemencoding`).

.. c:function:: struct _node* PyParser_SimpleParseFile(FILE *fp, const char *filename, int start)

 This is a simplified interface to :c:func:`PyParser_SimpleParseFileFlags` below,
 leaving *flags* set to ``0``.

.. c:function:: struct _node* PyParser_SimpleParseFileFlags(FILE *fp, const char *filename, int start, int flags)

 Similar to :c:func:`PyParser_SimpleParseStringFlagsFilename`, but the Python
 source code is read from *fp* instead of an in-memory string.

.. 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 filesystem encoding (:func:`sys.getfilesystemencoding`).
 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 filesystem encoding (:func:`os.fsdecode`).

 .. 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:type:: PyFrameObject

 The C structure of the objects used to describe frame objects. The
 fields of this type are subject to change at any time.

.. 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. 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:`~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:type:: 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;
 }

.. 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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