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 "Py_eval_input",
"Py_file_input", "Py_single_input", and "Py_func_type_input".  These
are described following the functions which accept them as parameters.

Note also that several of these functions take FILE* parameters.  One
particular issue which needs to be handled carefully is that the
"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 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.

int PyRun_AnyFile(FILE *fp, const char *filename)

   This is a simplified interface to "PyRun_AnyFileExFlags()" below,
   leaving *closeit* set to "0" and *flags* set to "NULL".

int PyRun_AnyFileFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

   This is a simplified interface to "PyRun_AnyFileExFlags()" below,
   leaving the *closeit* argument set to "0".

int PyRun_AnyFileEx(FILE *fp, const char *filename, int closeit)

   This is a simplified interface to "PyRun_AnyFileExFlags()" below,
   leaving the *flags* argument set to "NULL".

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 "PyRun_InteractiveLoop()", otherwise return the result of
   "PyRun_SimpleFile()".  *filename* is decoded from the filesystem
   encoding ("sys.getfilesystemencoding()").  If *filename* is "NULL",
   this function uses ""???"" as the filename. If *closeit* is true,
   the file is closed before "PyRun_SimpleFileExFlags()" returns.

int PyRun_SimpleString(const char *command)

   This is a simplified interface to "PyRun_SimpleStringFlags()"
   below, leaving the "PyCompilerFlags"* argument set to "NULL".

int PyRun_SimpleStringFlags(const char *command, PyCompilerFlags *flags)

   Executes the Python source code from *command* in the "__main__"
   module according to the *flags* argument. If "__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 "SystemExit" is raised, this
   function will not return "-1", but exit the process, as long as
   "PyConfig.inspect" is zero.

int PyRun_SimpleFile(FILE *fp, const char *filename)

   This is a simplified interface to "PyRun_SimpleFileExFlags()"
   below, leaving *closeit* set to "0" and *flags* set to "NULL".

int PyRun_SimpleFileEx(FILE *fp, const char *filename, int closeit)

   This is a simplified interface to "PyRun_SimpleFileExFlags()"
   below, leaving *flags* set to "NULL".

int PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)

   Similar to "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 *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.

int PyRun_InteractiveOneObject(FILE *fp, PyObject *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* must be
   a Python "str" object.

   Returns "0" when the input was executed successfully, "-1" if there
   was an exception, or an error code from the "errcode.h" include
   file distributed as part of Python if there was a parse error.
   (Note that "errcode.h" is not included by "Python.h", so must be
   included specifically if needed.)

int PyRun_InteractiveOne(FILE *fp, const char *filename)

   This is a simplified interface to "PyRun_InteractiveOneFlags()"
   below, leaving *flags* set to "NULL".

int PyRun_InteractiveOneFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)

   Similar to "PyRun_InteractiveOneObject()", but *filename* is a
   const char*, which is decoded from the *filesystem encoding and
   error handler*.

int PyRun_InteractiveLoop(FILE *fp, const char *filename)

   This is a simplified interface to "PyRun_InteractiveLoopFlags()"
   below, leaving *flags* set to "NULL".

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 and error handler*.  Returns "0" at EOF or a
   negative number upon failure.

int (*PyOS_InputHook)(void)
    * Part of the Stable ABI.*

   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 "Modules/_tkinter.c" in the Python source code.

   Changed in version 3.12: This function is only called from the main
   interpreter.

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 "readline" module sets this hook to
   provide line-editing and tab-completion features.

   The result must be a string allocated by "PyMem_RawMalloc()" or
   "PyMem_RawRealloc()", or "NULL" if an error occurred.

   Changed in version 3.4: The result must be allocated by
   "PyMem_RawMalloc()" or "PyMem_RawRealloc()", instead of being
   allocated by "PyMem_Malloc()" or "PyMem_Realloc()".

   Changed in version 3.12: This function is only called from the main
   interpreter.

PyObject *PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
    *Return value: New reference.*

   This is a simplified interface to "PyRun_StringFlags()" below,
   leaving *flags* set to "NULL".

PyObject *PyRun_StringFlags(const char *str, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
    *Return value: New reference.*

   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 symbol and must be one of the available
   start symbols.

   Returns the result of executing the code as a Python object, or
   "NULL" if an exception was raised.

PyObject *PyRun_File(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals)
    *Return value: New reference.*

   This is a simplified interface to "PyRun_FileExFlags()" below,
   leaving *closeit* set to "0" and *flags* set to "NULL".

PyObject *PyRun_FileEx(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit)
    *Return value: New reference.*

   This is a simplified interface to "PyRun_FileExFlags()" below,
   leaving *flags* set to "NULL".

PyObject *PyRun_FileFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, PyCompilerFlags *flags)
    *Return value: New reference.*

   This is a simplified interface to "PyRun_FileExFlags()" below,
   leaving *closeit* set to "0".

PyObject *PyRun_FileExFlags(FILE *fp, const char *filename, int start, PyObject *globals, PyObject *locals, int closeit, PyCompilerFlags *flags)
    *Return value: New reference.*

   Similar to "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
   and error handler*. If *closeit* is true, the file is closed before
   "PyRun_FileExFlags()" returns.

PyObject *Py_CompileString(const char *str, const char *filename, int start)
    *Return value: New reference.** Part of the Stable ABI.*

   This is a simplified interface to "Py_CompileStringFlags()" below,
   leaving *flags* set to "NULL".

PyObject *Py_CompileStringFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags)
    *Return value: New reference.*

   This is a simplified interface to "Py_CompileStringExFlags()"
   below, with *optimize* set to "-1".

PyObject *Py_CompileStringObject(const char *str, PyObject *filename, int start, PyCompilerFlags *flags, int optimize)
    *Return value: New reference.*

   Parse and compile the Python source code in *str*, returning the
   resulting code object.  The start symbol is given by *start*; this
   can be used to constrain the code which can be compiled and should
   be available start symbols.  The filename specified by *filename*
   is used to construct the code object and may appear in tracebacks
   or "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 "-O" options.  Explicit levels are "0" (no
   optimization; "__debug__" is true), "1" (asserts are removed,
   "__debug__" is false) or "2" (docstrings are removed too).

   Added in version 3.4.

PyObject *Py_CompileStringExFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags, int optimize)
    *Return value: New reference.*

   Like "Py_CompileStringObject()", but *filename* is a byte string
   decoded from the *filesystem encoding and error handler*.

   Added in version 3.2.

PyObject *PyEval_EvalCode(PyObject *co, PyObject *globals, PyObject *locals)
    *Return value: New reference.** Part of the Stable ABI.*

   This is a simplified interface to "PyEval_EvalCodeEx()", with just
   the code object, and global and local variables.  The other
   arguments are set to "NULL".

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)
    *Return value: New reference.** Part of the Stable ABI.*

   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 keyword-only arguments and a closure tuple of cells.

PyObject *PyEval_EvalFrame(PyFrameObject *f)
    *Return value: New reference.** Part of the Stable ABI.*

   Evaluate an execution frame.  This is a simplified interface to
   "PyEval_EvalFrameEx()", for backward compatibility.

PyObject *PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
    *Return value: New reference.** Part of the Stable ABI.*

   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 "throw()" methods of generator objects.

   Changed in version 3.4: This function now includes a debug
   assertion to help ensure that it does not silently discard an
   active exception.

int PyEval_MergeCompilerFlags(PyCompilerFlags *cf)

   This function changes the flags of the current evaluation frame,
   and returns true on success, false on failure.

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", "cf_flags" is treated
   as equal to "0", and any modification due to "from __future__
   import" is discarded.

   int cf_flags

      Compiler flags.

   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".

   Changed in version 3.8: Added *cf_feature_version* field.

   The available compiler flags are accessible as macros:

   PyCF_ALLOW_TOP_LEVEL_AWAIT
   PyCF_ONLY_AST
   PyCF_OPTIMIZED_AST
   PyCF_TYPE_COMMENTS

      See compiler flags in documentation of the "ast" Python module,
      which exports these constants under the same names.

   -[ Low-level flags ]-

   The following flags and masks serve narrow needs of the standard
   library and interactive interpreters.  Code outside the standard
   library rarely has a reason to use them.  They are considered
   implementation details and may change at any time.

   PyCF_ALLOW_INCOMPLETE_INPUT

      This flag is a private interface between the compiler and the
      "codeop" module.  Do not use it; its behavior is unsupported and
      may change without warning.

      With this flag set, when compilation fails because the source
      text ends where more input is expected, for example in the
      middle of an indented block or an unterminated string literal,
      the error raised is the undocumented "_IncompleteInputError", a
      subclass of "SyntaxError".  The "codeop" module sets this flag,
      together with "PyCF_DONT_IMPLY_DEDENT", to tell input that is
      incomplete apart from input with a real syntax error, so that
      interactive interpreters know when to prompt for another line
      instead of reporting an error.

      Added in version 3.11.

   PyCF_DONT_IMPLY_DEDENT

      By default, when compiling with the "Py_single_input" start
      symbol, reaching the end of the source text implicitly closes
      any open indented blocks.  With this flag set, open blocks are
      only closed if the last line of the source ends with a newline;
      otherwise, compilation fails with a "SyntaxError":

         PyCompilerFlags flags = {
             .cf_flags = 0,
             .cf_feature_version = PY_MINOR_VERSION,
         };
         const char *source = "if a:\n    pass";

         /* The "if" block is closed implicitly;
            this returns a code object: */
         Py_CompileStringFlags(source, "<input>", Py_single_input, &flags);

         /* With the flag, this fails with a SyntaxError,
            because the last line does not end with a newline: */
         flags.cf_flags = PyCF_DONT_IMPLY_DEDENT;
         Py_CompileStringFlags(source, "<input>", Py_single_input, &flags);

      The "codeop" module uses this flag to detect incomplete
      interactive input.  While the user is still typing inside an
      indented block, the source does not yet end with a newline, so
      it fails to compile and the user is prompted for another line.

   PyCF_IGNORE_COOKIE

      Read the source text as UTF-8, ignoring its **PEP 263** encoding
      declaration (“coding cookie”), if any:

         PyCompilerFlags flags = {
             .cf_flags = 0,
             .cf_feature_version = PY_MINOR_VERSION,
         };
         const char *source = "# coding: latin-1\ns = '\xe9'\n";

         /* The coding cookie is honored: byte 0xE9 is decoded as
            Latin-1, and this returns a code object that sets s to "é": */
         Py_CompileStringFlags(source, "<input>", Py_file_input, &flags);

         /* With the flag, the cookie is ignored and compilation fails
            with a SyntaxError, because 0xE9 is not valid UTF-8: */
         flags.cf_flags = PyCF_IGNORE_COOKIE;
         Py_CompileStringFlags(source, "<input>", Py_file_input, &flags);

      The "compile()", "eval()" and "exec()" built-in functions set
      this flag when the source is a "str" object, because they pass
      the text to the parser encoded as UTF-8.

   PyCF_SOURCE_IS_UTF8

      Mark the source text as known to be UTF-8 encoded. The
      "compile()", "eval()" and "exec()" built-in functions set this
      flag, but it currently has no effect.

   The “"PyCF"” flags above can be combined with “"CO_FUTURE"” flags
   such as "CO_FUTURE_ANNOTATIONS" to enable features normally
   selectable using future statements. See Code Object Flags for a
   complete list.

   The following masks combine several flags:

   PyCF_MASK

      Bitmask of all "CO_FUTURE" flags (see Code Object Flags), which
      select features normally enabled by future statements. When code
      compiled with a "PyCompilerFlags *flags" argument contains a
      "from __future__ import" statement, the flag for the imported
      feature is added to *flags*, so that code executed later in the
      same context inherits it.

   PyCF_MASK_OBSOLETE

      Do not use this mask in new code.  It is kept only so that old
      code passing its flags to "compile()" keeps working.

      Bitmask of flags for obsolete future features that no longer
      have any effect.

   PyCF_COMPILE_MASK

      Bitmask of all "PyCF" flags that change how the source is
      compiled, such as "PyCF_ONLY_AST". The "compile()" built-in
      function uses this mask to validate its *flags* argument.


Available start symbols
=======================

int Py_eval_input

   The start symbol from the Python grammar for isolated expressions;
   for use with "Py_CompileString()".

int Py_file_input

   The start symbol from the Python grammar for sequences of
   statements as read from a file or other source; for use with
   "Py_CompileString()".  This is the symbol to use when compiling
   arbitrarily long Python source code.

int Py_single_input

   The start symbol from the Python grammar for a single statement;
   for use with "Py_CompileString()". This is the symbol used for the
   interactive interpreter loop.

int Py_func_type_input

   The start symbol from the Python grammar for a function type; for
   use with "Py_CompileString()". This is used to parse “signature
   type comments” from **PEP 484**.

   This requires the "PyCF_ONLY_AST" flag to be set.

   See also:

     * "ast.FunctionType"

     * **PEP 484**

   Added in version 3.8.


Stack Effects
=============

See also: "dis.stack_effect()"

PY_INVALID_STACK_EFFECT

   Sentinel value representing an invalid stack effect.

   This is currently equivalent to "INT_MAX".

   Added in version 3.8.

int PyCompile_OpcodeStackEffect(int opcode, int oparg)

   Compute the stack effect of *opcode* with argument *oparg*.

   On success, this function returns the stack effect; on failure,
   this returns "PY_INVALID_STACK_EFFECT".

   Added in version 3.4.

int PyCompile_OpcodeStackEffectWithJump(int opcode, int oparg, int jump)

   Similar to "PyCompile_OpcodeStackEffect()", but don’t include the
   stack effect of jumping if *jump* is zero.

   If *jump* is "0", this will not include the stack effect of
   jumping, but if *jump* is "1" or "-1", this will include it.

   On success, this function returns the stack effect; on failure,
   this returns "PY_INVALID_STACK_EFFECT".

   Added in version 3.8.
