2. The Very High Level Layer

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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 Py_Main(int argc, char **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 main() function. 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 the integer passed to the sys.exit() function, 1 if the interpreter exits due to an exception, or 2 if the parameter list does not represent a valid Python command line.

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.

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