Metadata-Version: 2.1
Name: stackprinter
Version: 0.2.2
Summary: Debug-friendly stack traces, with variable values and semantic highlighting
Home-page: https://github.com/cknd/stackprinter
Author: cknd
Author-email: ck-github@mailbox.org
License: UNKNOWN
Description: <img src="https://raw.githubusercontent.com/cknd/stackprinter/master/darkbg.png" width="500">
        
        # Better crash logs
        
        This prints tracebacks / call stacks with code context and the values of nearby variables. It answers most of the questions I'd ask an interactive debugger: Where in the code did it happen, what's in the relevant local variables, and why was _that_ function called with _those_ arguments.
        
        Basically, it's a more helpful version of Python's built-in crash message. It will either print to the console or give you a string for logging.
        
        ```bash
        pip install stackprinter
        ```
        ```python
        import stackprinter
        stackprinter.set_excepthook()
        ```
        
        ### Before
        ```
        Traceback (most recent call last):
          File "demo.py", line 10, in <module>
            dangerous_function(somelist + anotherlist)
          File "demo.py", line 4, in dangerous_function
            return sorted(blub, key=lambda xs: sum(xs))
          File "demo.py", line 4, in <lambda>
            return sorted(blub, key=lambda xs: sum(xs))
        TypeError: unsupported operand type(s) for +: 'int' and 'str'
        ```
        
        ### After
        ```
        File demo.py, line 10, in <module>
            8         somelist = [[1,2], [3,4]]
            9         anotherlist = [['5', 6]]
        --> 10        dangerous_function(somelist + anotherlist)
            11    except:
            ..................................................
             somelist = [[1, 2], [3, 4]]
             anotherlist = [['5', 6]]
            ..................................................
        
        File demo.py, line 4, in dangerous_function
            3     def dangerous_function(blub):
        --> 4         return sorted(blub, key=lambda xs: sum(xs))
            ..................................................
             blub = [[1, 2], [3, 4], ['5', 6]]
            ..................................................
        
        File demo.py, line 4, in <lambda>
            2
            3     def dangerous_function(blub):
        --> 4         return sorted(blub, key=lambda xs: sum(xs))
            5
            ..................................................
             xs = ['5', 6]
            ..................................................
        
        TypeError: unsupported operand type(s) for +: 'int' and 'str'
        ```
        I sometimes use it locally instead of a debugger, but mostly it helps me sleep when my code runs somewhere where the only debug tool is a log file (though it's not a fully-grown [error monitoring system](https://sentry.io/welcome/)).
        
        By default, it tries to be somewhat polite about screen space (showing only a few source lines & the function header, and only the variables in those lines, and only (?) 500 characters per variable). You can [configure](https://github.com/cknd/stackprinter/blob/master/stackprinter/__init__.py#L82-L127) exactly how verbose things should be.
        
        The default output is plain text, which is good when you're logging to a file. There's also a color mode 🌈, enabled by passing `style='darkbg'` or `style='lightbg'` (or `'darkbg2'`, `'darkbg3'`, `'lightbg2'`, `'lightbg3'`) to any of the functions below. (It's an attempt at [semantic highlighting](https://medium.com/@brianwill/making-semantic-highlighting-useful-9aeac92411df), i.e. the colors follow the variables instead of the syntax.)
        
        <img src="https://raw.githubusercontent.com/cknd/stackprinter/master/notebook.png" width="500">
        
        
        # Usage
        
        ## Exception logging
        To globally replace the default python crash message, call `set_excepthook()` somewhere. This will print any uncaught exception to stderr by default. You could also [make this permanent for your python installation](#making-it-stick).
        
        ```python
        import stackprinter
        stackprinter.set_excepthook(style='color')
        ```
        
        To see a specific exception, call [`show()`](https://github.com/cknd/stackprinter/blob/master/stackprinter/__init__.py#L154-L162) or [`format()`](https://github.com/cknd/stackprinter/blob/master/stackprinter/__init__.py#L28-L137) inside an `except` block. `show()` prints to stderr by default, `format()` returns a string, for custom logging.
        
        
        ```python
        try:
            something()
        except:
            # print the current exception to stderr:
            stackprinter.show()
        
            # ...or only get a string, e.g. for logging:
            logger.error(stackprinter.format())
        ```
        You can also pass exceptions explicitly.
        ```python
        # or explicitly grab a particular exception
        try:
            something()
        except ValueError as e:
            error_message = stackprinter.format(e)
        
        ```
        ```python
        # or collect exceptions in a little jar somewhere, to log them later
        try:
            something()
        except ValueError as e:
            errors.append(e)
        
        # later:
        for err in errors:
            message = stackprinter.format(err)
            logger.log(message)
        ```
        
        For some ideas how to integrate this more directly with the `logging` module, see [`demo_logging.py`](https://github.com/cknd/stackprinter/blob/master/demo_logging.py) and [`demo_logging_hack.py`](https://github.com/cknd/stackprinter/blob/master/demo_logging_hack.py).
        
        For more config etc, for now, [see the docstring of `format()`](https://github.com/cknd/stackprinter/blob/master/stackprinter/__init__.py#L82-L127).
        
        ## Printing the current call stack
        To see your own thread's current call stack, call `show` or `format` anywhere outside of exception handling.
        
        ```python
        stackprinter.show() # or format()
        ```
        
        ## Printing the stack of another thread
        To inspect the call stack of any other running thread:
        
        ```python
        thread = threading.Thread(target=something)
        thread.start()
        # (...)
        stackprinter.show(thread) # or format(thread)
        ```
        
        ## Tracing a piece of code
        
        More for curiosity than anything else, you can watch a piece of code execute step-by-step, printing a trace of all calls & returns 'live' as they are happening. Slows everything down though, of course.
        ```python
        with stackprinter.TracePrinter(style='darkbg2'):
            dosomething()
        ```
        
        or
        ```python
        tp = stackprinter.TracePrinter(style='darkbg2')
        tp.enable()
        dosomething()
        # (...) +1 million lines
        tp.disable()
        ```
        <img src="https://raw.githubusercontent.com/cknd/stackprinter/master/trace.png" width="300">
        
        ## Making it stick
        
        To permanently replace the crash message for your python installation, you *could* put a file `sitecustomize.py` into the `site-packages` directory under one of the paths revealed by `python -c "import site; print(site.PREFIXES)"`, with contents like this:
        
        ```python
            # in e.g. some_virtualenv/lib/python3.x/site-packages/sitecustomize.py:
            import stackprinter
            stackprinter.set_excepthook(style='darkbg2')
        ```
        
        That would give you colorful tracebacks automatically every time, even in the REPL.
        
        (You could do a similar thing for IPython, [but they have their own method](https://ipython.readthedocs.io/en/stable/interactive/tutorial.html?highlight=startup#configuration), where the file goes into `~/.ipython/profile_default/startup` instead, and also I don't want to talk about what this module does to set an excepthook under IPython.)
        
        # How it works
        
        Basically, this is a frame formatter. For each [frame on the call stack](https://en.wikipedia.org/wiki/Call_stack), it grabs the source code to find out which source lines reference which variables. Then it displays code and variables in the neighbourhood of the last executed line.
        
        Since this already requires a map of where each variable occurs in the code, it was difficult not to also implement the whole semantic highlighting color thing seen in the screenshots. The colors are ANSI escape codes now, but it should be fairly straightforward™ to render the underlying data without any 1980ies terminal technology. Say, a foldable and clickable HTML page with downloadable pickled variables. For now you'll have to pipe the ANSI strings through [ansi2html](https://github.com/ralphbean/ansi2html/) or something.
        
        The format and everything is inspired by the excellent [`ultratb`](https://ipython.readthedocs.io/en/stable/api/generated/IPython.core.ultratb.html) in IPython. One day I'd like to contribute the whole "find out which variables in `locals` and `globals` are nearby in the source and print only those" machine over there, after trimming its complexity a bit.
        
        # Caveats
        
        This displays variable values as they are _at the time of formatting_. In
        multi-threaded programs, variables can change while we're busy walking
        the stack & printing them. So, if nothing seems to make sense, consider that
        your exception and the traceback messages are from slightly different times.
        Sadly, there is no responsible way to freeze all other threads as soon
        as we want to inspect some thread's call stack (...or is there?)
        
        # Docs
        
        \*coughs\*
        
        For now, just look at all the doc strings, [e.g. those of `format()`](https://github.com/cknd/stackprinter/blob/master/stackprinter/__init__.py#L28-L137)
        
Platform: UNKNOWN
Classifier: Programming Language :: Python :: 3
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Requires-Python: >=3.4
Description-Content-Type: text/markdown
