sys.stdin sys.stdout sys.stderr File objects used by the interpreter for standard input, output and errors: stdin is used for all interactive input (including calls to input()); stdout is used for the output of print() and expression statements and for the prompts of input(); The interpreter’s own prompts and its error messages go to stderr. These streams are regular text files like those returned by the open() function. Their parameters are chosen as follows: The character encoding is p

sys.stderr File objects used by the interpreter for standard input, output and errors: stdin is used for all interactive input (including calls to input()); stdout is used for the output of print() and expression statements and for the prompts of input(); The interpreter’s own prompts and its error messages go to stderr. These streams are regular text files like those returned by the open() function. Their parameters are chosen as follows: The character encoding is platform-dependent. U

sys.set_coroutine_wrapper(wrapper) Allows intercepting creation of coroutine objects (only ones that are created by an async def function; generators decorated with types.coroutine() or asyncio.coroutine() will not be intercepted). The wrapper argument must be either: a callable that accepts one argument (a coroutine object); None, to reset the wrapper. If called twice, the new wrapper replaces the previous one. The function is thread-specific. The wrapper callable cannot define new corou

sys.settscdump(on_flag) Activate dumping of VM measurements using the Pentium timestamp counter, if on_flag is true. Deactivate these dumps if on_flag is off. The function is available only if Python was compiled with --with-tsc. To understand the output of this dump, read Python/ceval.c in the Python sources. CPython implementation detail: This function is intimately bound to CPython implementation details and thus not likely to be implemented elsewhere.

sys.settrace(tracefunc) Set the system’s trace function, which allows you to implement a Python source code debugger in Python. The function is thread-specific; for a debugger to support multiple threads, it must be registered using settrace() for each thread being debugged. Trace functions should have three arguments: frame, event, and arg. frame is the current stack frame. event is a string: 'call', 'line', 'return', 'exception', 'c_call', 'c_return', or 'c_exception'. arg depends on the e

sys.setswitchinterval(interval) Set the interpreter’s thread switch interval (in seconds). This floating-point value determines the ideal duration of the “timeslices” allocated to concurrently running Python threads. Please note that the actual value can be higher, especially if long-running internal functions or methods are used. Also, which thread becomes scheduled at the end of the interval is the operating system’s decision. The interpreter doesn’t have its own scheduler. New in version

sys.setrecursionlimit(limit) Set the maximum depth of the Python interpreter stack to limit. This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python. The highest possible limit is platform-dependent. A user may need to set the limit higher when they have a program that requires deep recursion and a platform that supports a higher limit. This should be done with care, because a too-high limit can lead to a crash. If the new limit is too low at the cu

sys.setprofile(profilefunc) Set the system’s profile function, which allows you to implement a Python source code profiler in Python. See chapter The Python Profilers for more information on the Python profiler. The system’s profile function is called similarly to the system’s trace function (see settrace()), but it isn’t called for each executed line of code (only on call and return, but the return event is reported even when an exception has been set). The function is thread-specific, but

sys.setdlopenflags(n) Set the flags used by the interpreter for dlopen() calls, such as when the interpreter loads extension modules. Among other things, this will enable a lazy resolving of symbols when importing a module, if called as sys.setdlopenflags(0). To share symbols across extension modules, call as sys.setdlopenflags(os.RTLD_GLOBAL). Symbolic names for the flag values can be found in the os module (RTLD_xxx constants, e.g. os.RTLD_LAZY). Availability: Unix.

sys.setcheckinterval(interval) Set the interpreter’s “check interval”. This integer value determines how often the interpreter checks for periodic things such as thread switches and signal handlers. The default is 100, meaning the check is performed every 100 Python virtual instructions. Setting it to a larger value may increase performance for programs using threads. Setting it to a value <= 0 checks every virtual instruction, maximizing responsiveness as well as overhead. Deprecated si