# 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.
> This is a simplified interface to `PyRun_AnyFileExFlags` below, leaving *closeit* set to `0` and *flags* set to `NULL`.
> This is a simplified interface to `PyRun_AnyFileExFlags` below, leaving the *closeit* argument set to `0`.
> This is a simplified interface to `PyRun_AnyFileExFlags` below, leaving the *flags* argument set to `NULL`.
> 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.
> This is a simplified interface to `PyRun_SimpleStringFlags` below, leaving the `PyCompilerFlags`\* argument set to `NULL`.
> 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.
> This is a simplified interface to `PyRun_SimpleFileExFlags` below, leaving *closeit* set to `0` and *flags* set to `NULL`.
> This is a simplified interface to `PyRun_SimpleFileExFlags` below, leaving *flags* set to `NULL`.
> 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.
> 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.)
> This is a simplified interface to `PyRun_InteractiveOneFlags` below, leaving *flags* set to `NULL`.
> Similar to `PyRun_InteractiveOneObject`, but *filename* is a `const char*`, which is decoded from the `filesystem encoding and error handler`.
> This is a simplified interface to `PyRun_InteractiveLoopFlags` below, leaving *flags* set to `NULL`.
> 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.
> 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.
>
> The function is called without an `attached thread state`.
>
>
>
> 3.12 This function is only called from the `main interpreter `.
>
>
> Can be set to point to a function with the prototype `char *func(FILE *stdin, FILE *stdout, const 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 function is called without an `attached thread state`.
>
> If this pointer is `NULL`, `PyOS_Readline` sets it to the default implementation, `PyOS_Readline`, before reading input.
>
> The returned string must be null-terminated and include the trailing newline, if one was read. Return an empty string if the end of the file is reached before any characters are read. Return `NULL` on failure or interruption; a Python exception may be set.
>
> A non-`NULL` result must be a string allocated by `PyMem_RawMalloc` or `PyMem_RawRealloc`.
>
>
>
> 3.4 The result must be allocated by `PyMem_RawMalloc` or `PyMem_RawRealloc`, instead of being allocated by `PyMem_Malloc` or `PyMem_Realloc`.
>
>
>
>
>
> 3.12 This function is only called from the `main interpreter `.
>
>
> Display *prompt*, if it is not `NULL`, and read a line from *sys_stdin*. If both streams are terminals and the call is made from the `main interpreter `, use `PyOS_ReadlineFunctionPointer`. Otherwise, use the default implementation, which flushes *sys_stdout* and writes *prompt* to the C standard error stream.
>
> The returned string follows the contract of `PyOS_ReadlineFunctionPointer`, but the caller must free it with `PyMem_Free`. Return `NULL` on failure or interruption; a Python exception may be set.
> This is a simplified interface to `PyRun_StringFlags` below, leaving *flags* set to `NULL`.
> 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.
> This is a simplified interface to `PyRun_FileExFlags` below, leaving *closeit* set to `0` and *flags* set to `NULL`.
> This is a simplified interface to `PyRun_FileExFlags` below, leaving *flags* set to `NULL`.
> This is a simplified interface to `PyRun_FileExFlags` below, leaving *closeit* set to `0`.
> 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.
> This is a simplified interface to `Py_CompileStringFlags` below, leaving *flags* set to `NULL`.
> This is a simplified interface to `Py_CompileStringExFlags` below, with *optimize* set to `-1`.
> 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).
>
>
>
> 3.4
>
>
> Like `Py_CompileStringObject`, but *filename* is a byte string decoded from the `filesystem encoding and error handler`.
>
>
>
> 3.2
>
>
> 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`.
> 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.
> Evaluate an execution frame. This is a simplified interface to `PyEval_EvalFrameEx`, for backward compatibility.
> 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 `~generator.throw` methods of generator objects.
>
>
>
> 3.4 This function now includes a debug assertion to help ensure that it does not silently discard an active exception.
>
>
> This function changes the flags of the current evaluation frame, and returns true on success, false on failure.
> 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`, `~PyCompilerFlags.cf_flags` is treated as equal to `0`, and any modification due to `from __future__ import` is discarded.
>
> > Compiler flags.
>
> > *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 `~PyCompilerFlags.cf_flags`.
>
>
>
> 3.8 Added *cf_feature_version* field.
>
>
>
> The available compiler flags are accessible as macros:
>
> **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.
>
> > 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.
> >
> >
> >
> > 3.11
> >
> >
>
> > 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`:
> >
> > ``` c
> > 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, "", 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, "", 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.
>
> > Read the source text as UTF-8, ignoring its `263` encoding declaration ("coding cookie"), if any:
> >
> > ``` c
> > 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, "", 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, "", 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.
>
> > 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 `c_codeobject_flags` for a complete list.
>
> The following masks combine several flags:
>
> > Bitmask of all `CO_FUTURE` flags (see `c_codeobject_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.
>
> > 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.
>
> > 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
>
>
> single: Py_CompileString (C function)
>
>
>
> The start symbol from the Python grammar for isolated expressions; for use with `Py_CompileString`.
>
>
> single: Py_CompileString (C function)
>
>
>
> 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.
>
>
> single: Py_CompileString (C function)
>
>
>
> 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.
>
>
> single: Py_CompileString (C function)
>
>
>
> 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 `484`.
>
> This requires the `PyCF_ONLY_AST` flag to be set.
>
>
>
> \* `ast.FunctionType` \* `484`
>
>
>
>
>
> 3.8
>
>
## Stack Effects
`dis.stack_effect`
> Sentinel value representing an invalid stack effect.
>
> This is currently equivalent to `INT_MAX`.
>
>
>
> 3.8
>
>
> 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`.
>
>
>
> 3.4
>
>
> 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`.
>
>