初始化、定稿和线程 ¶

初始化和定稿解释器 ¶

void Py_Initialize ( ) ¶

Initialize the Python interpreter. In an application embedding Python, this should be called before using any other Python/C API functions; with the exception of Py_SetProgramName() , Py_SetPythonHome() and Py_SetPath() . This initializes the table of loaded modules ( sys.modules )，并创建基础模块 builtins , __main__ and sys 。它还初始化模块搜索路径 ( sys.path )。它不设置 sys.argv ；使用 PySys_SetArgvEx() for that. This is a no-op when called for a second time (without calling Py_FinalizeEx() first). There is no return value; it is a fatal error if the initialization fails.

注意

在 Windows，改变控制台模式从 O_TEXT to O_BINARY ，还会影响使用 C 运行时控制台的非 Python 使用。

void Py_InitializeEx ( int  initsigs ) ¶

此函数的工作像 Py_Initialize() if initsigs is 1 。若 initsigs is 0 , it skips initialization registration of signal handlers, which might be useful when Python is embedded.

int Py_IsInitialized ( ) ¶

Return true (nonzero) when the Python interpreter has been initialized, false (zero) if not. After Py_FinalizeEx() is called, this returns false until Py_Initialize() is called again.

int Py_FinalizeEx ( ) ¶

Undo all initializations made by Py_Initialize() and subsequent use of Python/C API functions, and destroy all sub-interpreters (see Py_NewInterpreter() below) that were created and not yet destroyed since the last call to Py_Initialize() . Ideally, this frees all memory allocated by the Python interpreter. This is a no-op when called for a second time (without calling Py_Initialize() again first). Normally the return value is 0 . If there were errors during finalization (flushing buffered data), -1 被返回。

This function is provided for a number of reasons. An embedding application might want to restart Python without having to restart the application itself. An application that has loaded the Python interpreter from a dynamically loadable library (or DLL) might want to free all memory allocated by Python before unloading the DLL. During a hunt for memory leaks in an application a developer might want to free all memory allocated by Python before exiting from the application.

Bugs and caveats: The destruction of modules and objects in modules is done in random order; this may cause destructors ( __del__() methods) to fail when they depend on other objects (even functions) or modules. Dynamically loaded extension modules loaded by Python are not unloaded. Small amounts of memory allocated by the Python interpreter may not be freed (if you find a leak, please report it). Memory tied up in circular references between objects is not freed. Some memory allocated by extension modules may not be freed. Some extensions may not work properly if their initialization routine is called more than once; this can happen if an application calls Py_Initialize() and Py_FinalizeEx() more than once.

3.6 版新增。

void Py_Finalize ( ) ¶

This is a backwards-compatible version of Py_FinalizeEx() that disregards the return value.

进程范围参数 ¶

int Py_SetStandardStreamEncoding ( const char  *encoding , const char  *errors ) ¶

此函数应该被调用先于 Py_Initialize() , if it is called at all. It specifies which encoding and error handling to use with standard IO, with the same meanings as in str.encode() .

它覆盖 PYTHONIOENCODING values, and allows embedding code to control IO encoding when the environment variable does not work.

encoding and/or errors may be NULL to use PYTHONIOENCODING and/or default values (depending on other settings).

注意， sys.stderr always uses the “backslashreplace” error handler, regardless of this (or any other) setting.

若 Py_FinalizeEx() is called, this function will need to be called again in order to affect subsequent calls to Py_Initialize() .

返回 0 if successful, a nonzero value on error (e.g. calling after the interpreter has already been initialized).

3.4 版新增。

void Py_SetProgramName ( wchar_t  *name ) ¶

此函数应该被调用先于 Py_Initialize() is called for the first time, if it is called at all. It tells the interpreter the value of the argv[0] 自变量到 main() function of the program (converted to wide characters). This is used by Py_GetPath() and some other functions below to find the Python run-time libraries relative to the interpreter executable. The default value is 'python' . The argument should point to a zero-terminated wide character string in static storage whose contents will not change for the duration of the program’s execution. No code in the Python interpreter will change the contents of this storage.

使用 Py_DecodeLocale() 来解码字节字符串以获取 wchar_* 字符串。

wchar* Py_GetProgramName ( ) ¶

返回的程序名设置采用 Py_SetProgramName() , or the default. The returned string points into static storage; the caller should not modify its value.

wchar_t* Py_GetPrefix ( ) ¶

返回 prefix for installed platform-independent files. This is derived through a number of complicated rules from the program name set with Py_SetProgramName() and some environment variables; for example, if the program name is '/usr/local/bin/python' , the prefix is '/usr/local' . The returned string points into static storage; the caller should not modify its value. This corresponds to the prefix variable in the top-level Makefile 和 --prefix 自变量到 configure script at build time. The value is available to Python code as sys.prefix . It is only useful on Unix. See also the next function.

wchar_t* Py_GetExecPrefix ( ) ¶

返回 exec-prefix for installed platform- dependent files. This is derived through a number of complicated rules from the program name set with Py_SetProgramName() and some environment variables; for example, if the program name is '/usr/local/bin/python' , the exec-prefix is '/usr/local' . The returned string points into static storage; the caller should not modify its value. This corresponds to the exec_prefix variable in the top-level Makefile 和 --exec-prefix 自变量到 configure script at build time. The value is available to Python code as sys.exec_prefix . It is only useful on Unix.

Background: The exec-prefix differs from the prefix when platform dependent files (such as executables and shared libraries) are installed in a different directory tree. In a typical installation, platform dependent files may be installed in the /usr/local/plat subtree while platform independent may be installed in /usr/local .

Generally speaking, a platform is a combination of hardware and software families, e.g. Sparc machines running the Solaris 2.x operating system are considered the same platform, but Intel machines running Solaris 2.x are another platform, and Intel machines running Linux are yet another platform. Different major revisions of the same operating system generally also form different platforms. Non-Unix operating systems are a different story; the installation strategies on those systems are so different that the prefix and exec-prefix are meaningless, and set to the empty string. Note that compiled Python bytecode files are platform independent (but not independent from the Python version by which they were compiled!).

System administrators will know how to configure the mount or automount programs to share /usr/local between platforms while having /usr/local/plat be a different filesystem for each platform.

wchar_t* Py_GetProgramFullPath ( ) ¶

Return the full program name of the Python executable; this is computed as a side-effect of deriving the default module search path from the program name (set by Py_SetProgramName() above). The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.executable .

wchar_t* Py_GetPath ( ) ¶

Return the default module search path; this is computed from the program name (set by Py_SetProgramName() above) and some environment variables. The returned string consists of a series of directory names separated by a platform dependent delimiter character. The delimiter character is ':' on Unix and Mac OS X, ';' on Windows. The returned string points into static storage; the caller should not modify its value. The list sys.path is initialized with this value on interpreter startup; it can be (and usually is) modified later to change the search path for loading modules.

void Py_SetPath ( const wchar_t  * ) ¶

Set the default module search path. If this function is called before Py_Initialize() ，那么 Py_GetPath() won’t attempt to compute a default search path but uses the one provided instead. This is useful if Python is embedded by an application that has full knowledge of the location of all modules. The path components should be separated by the platform dependent delimiter character, which is ':' on Unix and Mac OS X, ';' 在 Windows。

This also causes sys.executable to be set only to the raw program name (see Py_SetProgramName() ) and for sys.prefix and sys.exec_prefix to be empty. It is up to the caller to modify these if required after calling Py_Initialize() .

使用 Py_DecodeLocale() 来解码字节字符串以获取 wchar_* 字符串。

The path argument is copied internally, so the caller may free it after the call completes.

const char* Py_GetVersion ( ) ¶

Return the version of this Python interpreter. This is a string that looks something like

"3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) \n[GCC 4.2.3]"
										

The first word (up to the first space character) is the current Python version; the first three characters are the major and minor version separated by a period. The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.version .

const char* Py_GetPlatform ( ) ¶

Return the platform identifier for the current platform. On Unix, this is formed from the “official” name of the operating system, converted to lower case, followed by the major revision number; e.g., for Solaris 2.x, which is also known as SunOS 5.x, the value is 'sunos5' . On Mac OS X, it is 'darwin' . On Windows, it is 'win' . The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.platform .

const char* Py_GetCopyright ( ) ¶

Return the official copyright string for the current Python version, for example

'Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam'

The returned string points into static storage; the caller should not modify its value. The value is available to Python code as sys.copyright .

const char* Py_GetCompiler ( ) ¶

Return an indication of the compiler used to build the current Python version, in square brackets, for example:

"[GCC 2.7.2.2]"
										

The returned string points into static storage; the caller should not modify its value. The value is available to Python code as part of the variable sys.version .

const char* Py_GetBuildInfo ( ) ¶

Return information about the sequence number and build date and time of the current Python interpreter instance, for example

"#67, Aug  1 1997, 22:34:28"
										

The returned string points into static storage; the caller should not modify its value. The value is available to Python code as part of the variable sys.version .

void PySys_SetArgvEx ( int  argc , wchar_t  **argv , int  updatepath ) ¶

Set sys.argv 基于 argc and argv . These parameters are similar to those passed to the program’s main() function with the difference that the first entry should refer to the script file to be executed rather than the executable hosting the Python interpreter. If there isn’t a script that will be run, the first entry in argv can be an empty string. If this function fails to initialize sys.argv , a fatal condition is signalled using Py_FatalError() .

若 updatepath is zero, this is all the function does. If updatepath is non-zero, the function also modifies sys.path according to the following algorithm:

• If the name of an existing script is passed in argv[0] , the absolute path of the directory where the script is located is prepended to sys.path .
• Otherwise (that is, if argc is 0 or argv[0] doesn’t point to an existing file name), an empty string is prepended to sys.path , which is the same as prepending the current working directory ( "." ).

使用 Py_DecodeLocale() 来解码字节字符串以获取 wchar_* 字符串。

注意

It is recommended that applications embedding the Python interpreter for purposes other than executing a single script pass 0 as updatepath , and update sys.path themselves if desired. See CVE-2008-5983 .

On versions before 3.1.3, you can achieve the same effect by manually popping the first sys.path element after having called PySys_SetArgv() ，例如使用：

PyRun_SimpleString("import sys; sys.path.pop(0)\n");
											

3.1.3 版新增。

void PySys_SetArgv ( int  argc , wchar_t  **argv ) ¶

此函数的工作像 PySys_SetArgvEx() with updatepath 设为 1 除非 python 解释器的开始是采用 -I .

使用 Py_DecodeLocale() 来解码字节字符串以获取 wchar_* 字符串。

3.4 版改变： updatepath 值从属 -I .

void Py_SetPythonHome ( wchar_t  *home ) ¶

Set the default “home” directory, that is, the location of the standard Python libraries. See PYTHONHOME for the meaning of the argument string.

The argument should point to a zero-terminated character string in static storage whose contents will not change for the duration of the program’s execution. No code in the Python interpreter will change the contents of this storage.

使用 Py_DecodeLocale() 来解码字节字符串以获取 wchar_* 字符串。

w_char* Py_GetPythonHome ( ) ¶

Return the default “home”, that is, the value set by a previous call to Py_SetPythonHome() , or the value of the PYTHONHOME environment variable if it is set.

线程状态和 GIL (全局解释器锁) ¶

The Python interpreter is not fully thread-safe. In order to support multi-threaded Python programs, there’s a global lock, called the 全局解释器锁 or GIL , that must be held by the current thread before it can safely access Python objects. Without the lock, even the simplest operations could cause problems in a multi-threaded program: for example, when two threads simultaneously increment the reference count of the same object, the reference count could end up being incremented only once instead of twice.

Therefore, the rule exists that only the thread that has acquired the GIL may operate on Python objects or call Python/C API functions. In order to emulate concurrency of execution, the interpreter regularly tries to switch threads (see sys.setswitchinterval() ). The lock is also released around potentially blocking I/O operations like reading or writing a file, so that other Python threads can run in the meantime.

The Python interpreter keeps some thread-specific bookkeeping information inside a data structure called PyThreadState . There’s also one global variable pointing to the current PyThreadState : it can be retrieved using PyThreadState_Get() .

Save the thread state in a local variable.
Release the global interpreter lock.
... Do some blocking I/O operation ...
Reacquire the global interpreter lock.
Restore the thread state from the local variable.
									

Py_BEGIN_ALLOW_THREADS
... Do some blocking I/O operation ...
Py_END_ALLOW_THREADS
									

PyThreadState *_save;
_save = PyEval_SaveThread();
...Do some blocking I/O operation...
PyEval_RestoreThread(_save);
									

PyGILState_STATE gstate;
gstate = PyGILState_Ensure();
/* Perform Python actions here. */
result = CallSomeFunction();
/* evaluate result or handle exception */
/* Release the thread. No Python API allowed beyond this point. */
PyGILState_Release(gstate);
									

子解释器支持 ¶

While in most uses, you will only embed a single Python interpreter, there are cases where you need to create several independent interpreters in the same process and perhaps even in the same thread. Sub-interpreters allow you to do that. You can switch between sub-interpreters using the PyThreadState_Swap() function. You can create and destroy them using the following functions:

PyThreadState * Py_NewInterpreter ( ) ¶

Create a new sub-interpreter. This is an (almost) totally separate environment for the execution of Python code. In particular, the new interpreter has separate, independent versions of all imported modules, including the fundamental modules builtins , __main__ and sys . The table of loaded modules ( sys.modules ) and the module search path ( sys.path ) are also separate. The new environment has no sys.argv variable. It has new standard I/O stream file objects sys.stdin , sys.stdout and sys.stderr (however these refer to the same underlying file descriptors).

The return value points to the first thread state created in the new sub-interpreter. This thread state is made in the current thread state. Note that no actual thread is created; see the discussion of thread states below. If creation of the new interpreter is unsuccessful, NULL is returned; no exception is set since the exception state is stored in the current thread state and there may not be a current thread state. (Like all other Python/C API functions, the global interpreter lock must be held before calling this function and is still held when it returns; however, unlike most other Python/C API functions, there needn’t be a current thread state on entry.)

Extension modules are shared between (sub-)interpreters as follows: the first time a particular extension is imported, it is initialized normally, and a (shallow) copy of its module’s dictionary is squirreled away. When the same extension is imported by another (sub-)interpreter, a new module is initialized and filled with the contents of this copy; the extension’s init function is not called. Note that this is different from what happens when an extension is imported after the interpreter has been completely re-initialized by calling Py_FinalizeEx() and Py_Initialize() ; in that case, the extension’s initmodule function is called again.

void Py_EndInterpreter ( PyThreadState  *tstate ) ¶

Destroy the (sub-)interpreter represented by the given thread state. The given thread state must be the current thread state. See the discussion of thread states below. When the call returns, the current thread state is NULL . All thread states associated with this interpreter are destroyed. (The global interpreter lock must be held before calling this function and is still held when it returns.) Py_FinalizeEx() will destroy all sub-interpreters that haven’t been explicitly destroyed at that point.

异步通知 ¶

A mechanism is provided to make asynchronous notifications to the main interpreter thread. These notifications take the form of a function pointer and a void pointer argument.

int Py_AddPendingCall ( int ( *func )(void *), void  *arg ) ¶

Schedule a function to be called from the main interpreter thread. On success, 0 is returned and func is queued for being called in the main thread. On failure, -1 is returned without setting any exception.

When successfully queued, func 将是 eventually called from the main interpreter thread with the argument arg . It will be called asynchronously with respect to normally running Python code, but with both these conditions met:

• 在 bytecode boundary;
• with the main thread holding the 全局解释器锁 ( func can therefore use the full C API).

func must return 0 on success, or -1 on failure with an exception set. func won’t be interrupted to perform another asynchronous notification recursively, but it can still be interrupted to switch threads if the global interpreter lock is released.

This function doesn’t need a current thread state to run, and it doesn’t need the global interpreter lock.

警告

This is a low-level function, only useful for very special cases. There is no guarantee that func will be called as quick as possible. If the main thread is busy executing a system call, func won’t be called before the system call returns. This function is generally not suitable for calling Python code from arbitrary C threads. Instead, use the PyGILState API .

3.1 版新增。

剖析和跟踪 ¶

The Python interpreter provides some low-level support for attaching profiling and execution tracing facilities. These are used for profiling, debugging, and coverage analysis tools.

This C interface allows the profiling or tracing code to avoid the overhead of calling through Python-level callable objects, making a direct C function call instead. The essential attributes of the facility have not changed; the interface allows trace functions to be installed per-thread, and the basic events reported to the trace function are the same as had been reported to the Python-level trace functions in previous versions.

int (*Py_tracefunc) ( PyObject  *obj , PyFrameObject  *frame , int  what , PyObject  *arg ) ¶

The type of the trace function registered using PyEval_SetProfile() and PyEval_SetTrace() . The first parameter is the object passed to the registration function as obj , frame is the frame object to which the event pertains, what is one of the constants PyTrace_CALL , PyTrace_EXCEPTION , PyTrace_LINE , PyTrace_RETURN , PyTrace_C_CALL , PyTrace_C_EXCEPTION ，或 PyTrace_C_RETURN ，和 arg depends on the value of what :

Value of what	Meaning of arg
PyTrace_CALL	Always Py_None .
PyTrace_EXCEPTION	Exception information as returned by sys.exc_info() .
PyTrace_LINE	Always Py_None .
PyTrace_RETURN	Value being returned to the caller, or NULL if caused by an exception.
PyTrace_C_CALL	Function object being called.
PyTrace_C_EXCEPTION	Function object being called.
PyTrace_C_RETURN	Function object being called.

int PyTrace_CALL ¶

The value of the what parameter to a Py_tracefunc function when a new call to a function or method is being reported, or a new entry into a generator. Note that the creation of the iterator for a generator function is not reported as there is no control transfer to the Python bytecode in the corresponding frame.

int PyTrace_EXCEPTION ¶

The value of the what parameter to a Py_tracefunc function when an exception has been raised. The callback function is called with this value for what when after any bytecode is processed after which the exception becomes set within the frame being executed. The effect of this is that as exception propagation causes the Python stack to unwind, the callback is called upon return to each frame as the exception propagates. Only trace functions receives these events; they are not needed by the profiler.

int PyTrace_LINE ¶

The value passed as the what parameter to a trace function (but not a profiling function) when a line-number event is being reported.

int PyTrace_RETURN ¶

The value for the what 参数到 Py_tracefunc functions when a call is about to return.

int PyTrace_C_CALL ¶

The value for the what 参数到 Py_tracefunc functions when a C function is about to be called.

int PyTrace_C_EXCEPTION ¶

The value for the what 参数到 Py_tracefunc functions when a C function has raised an exception.

int PyTrace_C_RETURN ¶

The value for the what 参数到 Py_tracefunc functions when a C function has returned.

void PyEval_SetProfile ( Py_tracefunc  func , PyObject  *obj ) ¶

Set the profiler function to func 。 obj parameter is passed to the function as its first parameter, and may be any Python object, or NULL . If the profile function needs to maintain state, using a different value for obj for each thread provides a convenient and thread-safe place to store it. The profile function is called for all monitored events except PyTrace_LINE and PyTrace_EXCEPTION .

void PyEval_SetTrace ( Py_tracefunc  func , PyObject  *obj ) ¶

Set the tracing function to func . This is similar to PyEval_SetProfile() , except the tracing function does receive line-number events and does not receive any event related to C function objects being called. Any trace function registered using PyEval_SetTrace() will not receive PyTrace_C_CALL , PyTrace_C_EXCEPTION or PyTrace_C_RETURN as a value for the what 参数。

PyObject * PyEval_GetCallStats ( PyObject  *self ) ¶

Return a tuple of function call counts. There are constants defined for the positions within the tuple:

名称	值
PCALL_ALL	0
PCALL_FUNCTION	1
PCALL_FAST_FUNCTION	2
PCALL_FASTER_FUNCTION	3
PCALL_METHOD	4
PCALL_BOUND_METHOD	5
PCALL_CFUNCTION	6
PCALL_TYPE	7
PCALL_GENERATOR	8
PCALL_OTHER	9
PCALL_POP	10

PCALL_FAST_FUNCTION means no argument tuple needs to be created. PCALL_FASTER_FUNCTION means that the fast-path frame setup code is used.

If there is a method call where the call can be optimized by changing the argument tuple and calling the function directly, it gets recorded twice.

This function is only present if Python is compiled with CALL_PROFILE defined.

高级调试器支持 ¶

These functions are only intended to be used by advanced debugging tools.

PyInterpreterState * PyInterpreterState_Head ( ) ¶

Return the interpreter state object at the head of the list of all such objects.

PyInterpreterState * PyInterpreterState_Next ( PyInterpreterState  *interp ) ¶

Return the next interpreter state object after interp from the list of all such objects.

PyThreadState * PyInterpreterState_ThreadHead ( PyInterpreterState  *interp ) ¶

Return the pointer to the first PyThreadState object in the list of threads associated with the interpreter interp .

PyThreadState * PyThreadState_Next ( PyThreadState  *tstate ) ¶

Return the next thread state object after tstate from the list of all such objects belonging to the same PyInterpreterState 对象。