code — Interpreter base classes

Source code: Lib/code.py

The code module provides facilities to implement read-eval-print loops in Python. code模块提供了在Python中实现read-eval-print循环的工具。Two classes and convenience functions are included which can be used to build applications which provide an interactive interpreter prompt.包括两个类和便利函数，可用于构建提供交互式解释器提示的应用程序。

classcode.InteractiveInterpreter(locals=None)

This class deals with parsing and interpreter state (the user’s namespace); it does not deal with input buffering or prompting or input file naming (the filename is always passed in explicitly). 这个类处理解析和解释器状态（用户的命名空间）；它不处理输入缓冲或提示或输入文件命名（文件名总是显式传入的）。The optional locals argument specifies the dictionary in which code will be executed; it defaults to a newly created dictionary with key '__name__' set to '__console__' and key '__doc__' set to None.可选的locals参数指定将在其中执行代码的字典；它默认为新创建的字典，其中键'__name__'设置为'__console__'，键'__doc__'设置成None。

classcode.InteractiveConsole(locals=None, filename='<console>')

Closely emulate the behavior of the interactive Python interpreter. 密切模仿交互式Python解释器的行为。This class builds on InteractiveInterpreter and adds prompting using the familiar sys.ps1 and sys.ps2, and input buffering.该类构建在InteractiveInterpreter上，并使用熟悉的sys.ps1和sys.ps2以及输入缓冲添加提示。

code.interact(banner=None, readfunc=None, local=None, exitmsg=None)

Convenience function to run a read-eval-print loop. 运行读取评估打印循环的便利函数。This creates a new instance of InteractiveConsole and sets readfunc to be used as the InteractiveConsole.raw_input() method, if provided. 这将创建一个新的InteractiveConsole实例，并将readfunc设置为用作InteractiveConsole.raw_input()方法（如果提供）。If local is provided, it is passed to the InteractiveConsole constructor for use as the default namespace for the interpreter loop. 如果提供了local，它将被传递给InteractiveConsole构造函数，用作解释器循环的默认命名空间。The interact() method of the instance is then run with banner and exitmsg passed as the banner and exit message to use, if provided. 然后运行实例的interact()方法，并传递banner和exitmsg作为banner和退出消息（如果提供的话）。The console object is discarded after use.控制台对象在使用后将被丢弃。

Changed in version 3.6:版本3.6中更改： Added exitmsg parameter.

code.compile_command(source, filename='<input>', symbol='single')

This function is useful for programs that want to emulate Python’s interpreter main loop (a.k.a. the read-eval-print loop). 这个函数对于想要模拟Python解释器主循环（也称为read-eval-print循环）的程序非常有用。The tricky part is to determine when the user has entered an incomplete command that can be completed by entering more text (as opposed to a complete command or a syntax error). 棘手的部分是确定用户何时输入了一个不完整的命令，该命令可以通过输入更多文本来完成（而不是完整的命令或语法错误）。This function almost always makes the same decision as the real interpreter main loop.这个函数几乎总是做出与真正的解释器主循环相同的决定。

source is the source string; filename is the optional filename from which source was read, defaulting to '<input>'; and symbol is the optional grammar start symbol, which should be 'single' (the default), 'eval' or 'exec'.source是源字符串；filename是从中读取源的可选文件名，默认为'<input>'；symbol是可选的语法起始符号，应为'single'（默认值）、'eval'或'exec'。

Returns a code object (the same as compile(source, filename, symbol)) if the command is complete and valid; None if the command is incomplete; raises SyntaxError if the command is complete and contains a syntax error, or raises OverflowError or ValueError if the command contains an invalid literal.

Interactive Interpreter Objects

InteractiveInterpreter.runsource(source, filename='<input>', symbol='single')

Compile and run some source in the interpreter. Arguments are the same as for compile_command(); the default for filename is '<input>', and for symbol is 'single'. One of several things can happen:

The return value can be used to decide whether to use sys.ps1 or sys.ps2 to prompt the next line.

InteractiveInterpreter.runcode(code)

Execute a code object. When an exception occurs, showtraceback() is called to display a traceback. All exceptions are caught except SystemExit, which is allowed to propagate.

A note about KeyboardInterrupt: this exception may occur elsewhere in this code, and may not always be caught. The caller should be prepared to deal with it.

InteractiveInterpreter.showsyntaxerror(filename=None)

Display the syntax error that just occurred. This does not display a stack trace because there isn’t one for syntax errors. If filename is given, it is stuffed into the exception instead of the default filename provided by Python’s parser, because it always uses '<string>' when reading from a string. The output is written by the write() method.

InteractiveInterpreter.showtraceback()

Display the exception that just occurred. We remove the first stack item because it is within the interpreter object implementation. The output is written by the write() method.

Changed in version 3.5:版本3.5中更改： The full chained traceback is displayed instead of just the primary traceback.

InteractiveInterpreter.write(data)

Write a string to the standard error stream (sys.stderr). Derived classes should override this to provide the appropriate output handling as needed.

Interactive Console Objects

The InteractiveConsole class is a subclass of InteractiveInterpreter, and so offers all the methods of the interpreter objects as well as the following additions.

InteractiveConsole.interact(banner=None, exitmsg=None)

Closely emulate the interactive Python console. The optional banner argument specify the banner to print before the first interaction; by default it prints a banner similar to the one printed by the standard Python interpreter, followed by the class name of the console object in parentheses (so as not to confuse this with the real interpreter – since it’s so close!).

The optional exitmsg argument specifies an exit message printed when exiting. Pass the empty string to suppress the exit message. If exitmsg is not given or None, a default message is printed.

Changed in version 3.4:版本3.4中更改： To suppress printing any banner, pass an empty string.

Changed in version 3.6:版本3.6中更改： Print an exit message when exiting.

InteractiveConsole.push(line)

Push a line of source text to the interpreter. The line should not have a trailing newline; it may have internal newlines. The line is appended to a buffer and the interpreter’s runsource() method is called with the concatenated contents of the buffer as source. If this indicates that the command was executed or invalid, the buffer is reset; otherwise, the command is incomplete, and the buffer is left as it was after the line was appended. The return value is True if more input is required, False if the line was dealt with in some way (this is the same as runsource()).

InteractiveConsole.resetbuffer()

Remove any unhandled source text from the input buffer.

InteractiveConsole.raw_input(prompt='')

Write a prompt and read a line. The returned line does not include the trailing newline. When the user enters the EOF key sequence, EOFError is raised. The base implementation reads from sys.stdin; a subclass may replace this with a different implementation.