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.

intPyRun_AnyFile(FILE*fp, constchar*filename)

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

intPyRun_AnyFileFlags(FILE*fp, constchar*filename, PyCompilerFlags *flags)

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

intPyRun_AnyFileEx(FILE*fp, constchar*filename, intcloseit)

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

intPyRun_AnyFileExFlags(FILE*fp, constchar*filename, intcloseit, 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.

intPyRun_SimpleString(constchar*command)

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

intPyRun_SimpleStringFlags(constchar*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.

intPyRun_SimpleFile(FILE*fp, constchar*filename)

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

intPyRun_SimpleFileEx(FILE*fp, constchar*filename, intcloseit)

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

intPyRun_SimpleFileExFlags(FILE*fp, constchar*filename, intcloseit, 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.

intPyRun_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.)

intPyRun_InteractiveOne(FILE*fp, constchar*filename)

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

intPyRun_InteractiveOneFlags(FILE*fp, constchar*filename, PyCompilerFlags *flags)

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

intPyRun_InteractiveLoop(FILE*fp, constchar*filename)

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

intPyRun_InteractiveLoopFlags(FILE*fp, constchar*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*,constchar*)

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(constchar*str, intstart, 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(constchar*str, intstart, 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 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, constchar*filename, intstart, 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, constchar*filename, intstart, PyObject *globals, PyObject *locals, intcloseit)
Return value: New reference.

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

PyObject *PyRun_FileFlags(FILE*fp, constchar*filename, intstart, 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, constchar*filename, intstart, PyObject *globals, PyObject *locals, intcloseit, 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(constchar*str, constchar*filename, intstart)
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(constchar*str, constchar*filename, intstart, PyCompilerFlags *flags)
Return value: New reference.

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

PyObject *Py_CompileStringObject(constchar*str, PyObject *filename, intstart, PyCompilerFlags *flags, intoptimize)
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(constchar*str, constchar*filename, intstart, PyCompilerFlags *flags, intoptimize)
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, intargcount, PyObject *const*kws, intkwcount, PyObject *const*defs, intdefcount, 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, intthrowflag)
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.

intPyEval_MergeCompilerFlags(PyCompilerFlags *cf)

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

structPyCompilerFlags

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.

intcf_flags

Compiler flags.

intcf_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.

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.

Available start symbols

intPy_eval_input

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

intPy_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.

intPy_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.

intPy_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.

Added in version 3.8.

Stack Effects

PY_INVALID_STACK_EFFECT

Sentinel value representing an invalid stack effect.

This is currently equivalent to INT_MAX.

Added in version 3.8.

intPyCompile_OpcodeStackEffect(intopcode, intoparg)

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.

intPyCompile_OpcodeStackEffectWithJump(intopcode, intoparg, intjump)

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.