2. The Very High Level Layer
Keywords: api

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2. 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`, and `Py_single_input`. These are described following the functions which accept them as parameters.

Note also that several of these functions take `FILE*` parameters. On 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, char *filename)
  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()`. If filename is `NULL`, this function uses `"???"` as the filename.

int `PyRun_SimpleString` (char *command)
  Executes the Python source code from command in the `__main__` module. 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.

int `PyRun_SimpleFile` (FILE *fp, char *filename)
  Similar to `PyRun_SimpleString()`, but the Python source code is read from fp instead of an in-memory string. filename should be the name of the file.

int `PyRun_InteractiveOne` (FILE *fp, char *filename)
  Read and execute a single statement from a file associated with an interactive device. If filename is `NULL`, `"???"` is used instead. The user will be prompted using `sys.ps1` and `sys.ps2`. 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 in case of a parse error. (Note that errcode.h is not included by Python.h, so must be included specifically if needed.)

int `PyRun_InteractiveLoop` (FILE *fp, char *filename)
  Read and execute statements from a file associated with an interactive device until EOF is reached. If filename is `NULL`, `"???"` is used instead. The user will be prompted using `sys.ps1` and `sys.ps2`. Returns `0` at EOF.

struct _node* `PyParser_SimpleParseString` (char *str, int start)
  Parse Python source code from str using the start token start. 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.

struct _node* `PyParser_SimpleParseFile` (FILE *fp, char *filename, int start)
  Similar to `PyParser_SimpleParseString()`, but the Python source code is read from fp instead of an in-memory string. filename should be the name of the file.

PyObject* `PyRun_String` (char *str, int start, PyObject *globals, PyObject *locals)
  Return value: New reference.
  Execute Python source code from str in the context specified by the dictionaries globals and locals. 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.

PyObject* `PyRun_File` (FILE *fp, char *filename, int start, PyObject *globals, PyObject *locals)
  Return value: New reference.
  Similar to `PyRun_String()`, but the Python source code is read from fp instead of an in-memory string. filename should be the name of the file.

PyObject* `Py_CompileString` (char *str, char *filename, int start)
  Return value: New reference.
  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 `Py_eval_input`, `Py_file_input`, or `Py_single_input`. 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.

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.