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Python Tracebackplus
"""More comprehensive traceback formatting for Python scripts.
To enable this module, do:
import tracebackplus; tracebackplus.enable()
at the top of your script. The optional arguments to enable() are:
logdir - if set, tracebacks are written to files in this directory
context - number of lines of source code to show for each stack frame
By default, tracebacks are displayed but not saved and the context is 5 lines.
Alternatively, if you have caught an exception and want tracebackplus to display it
for you, call tracebackplus.handler(). The optional argument to handler() is a
3-item tuple (etype, evalue, etb) just like the value of sys.exc_info().
"""
'''
Licensing:
MIT License
Copyright (c) 2020 Kelly Brazil
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
tracebackplus was derived from the cgitb standard library module. As cgitb is being
deprecated, this simplified version of cgitb was created.
https://github.com/python/cpython/blob/3.8/Lib/cgitb.py
"Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Python Software Foundation;
All Rights Reserved"
PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
--------------------------------------------
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otherwise using this software ("Python") in source or binary form and
its associated documentation.
2. Subject to the terms and conditions of this License Agreement, PSF hereby
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distribute, and otherwise use Python alone or in any derivative version,
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2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Python Software Foundation;
All Rights Reserved" are retained in Python alone or in any derivative version
prepared by Licensee.
3. In the event Licensee prepares a derivative work that is based on
or incorporates Python or any part thereof, and wants to make
the derivative work available to others as provided herein, then
Licensee hereby agrees to include in any such work a brief summary of
the changes made to Python.
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DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON WILL NOT
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8. By copying, installing or otherwise using Python, Licensee
agrees to be bound by the terms and conditions of this License
Agreement.
'''
import inspect
import keyword
import linecache
import os
import pydoc
import sys
import tempfile
import time
import tokenize
import traceback
__UNDEF__ = [] # a special sentinel object
def lookup(name, frame, locals):
"""Find the value for a given name in the given environment."""
if name in locals:
return 'local', locals[name]
if name in frame.f_globals:
return 'global', frame.f_globals[name]
if '__builtins__' in frame.f_globals:
builtins = frame.f_globals['__builtins__']
if isinstance(builtins, dict):
if name in builtins:
return 'builtin', builtins[name]
else:
if hasattr(builtins, name):
return 'builtin', getattr(builtins, name)
return None, __UNDEF__
def scanvars(reader, frame, locals):
"""Scan one logical line of Python and look up values of variables used."""
vars, lasttoken, parent, prefix, value = [], None, None, '', __UNDEF__
for ttype, token, start, end, line in tokenize.generate_tokens(reader):
if ttype == tokenize.NEWLINE:
break
if ttype == tokenize.NAME and token not in keyword.kwlist:
if lasttoken == '.':
if parent is not __UNDEF__:
value = getattr(parent, token, __UNDEF__)
vars.append((prefix + token, prefix, value))
else:
where, value = lookup(token, frame, locals)
vars.append((token, where, value))
elif token == '.':
prefix += lasttoken + '.'
parent = value
else:
parent, prefix = None, ''
lasttoken = token
return vars
def text(einfo, context=5):
"""Return a plain text document describing a given traceback."""
etype, evalue, etb = einfo
if isinstance(etype, type):
etype = etype.__name__
pyver = 'Python ' + sys.version.split()[0] + ': ' + sys.executable
date = time.ctime(time.time())
head = '%s\n%s\n%s\n' % (str(etype), pyver, date) + '''
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
'''
frames = []
records = inspect.getinnerframes(etb, context)
for frame, file, lnum, func, lines, index in records:
file = file and os.path.abspath(file) or '?'
args, varargs, varkw, locals = inspect.getargvalues(frame)
call = ''
if func != '?':
call = 'in ' + func + \
inspect.formatargvalues(args, varargs, varkw, locals,
formatvalue=lambda value: '=' + pydoc.text.repr(value))
highlight = {}
def reader(lnum=[lnum]):
highlight[lnum[0]] = 1
try:
return linecache.getline(file, lnum[0])
finally:
lnum[0] += 1
vars = scanvars(reader, frame, locals)
rows = [' %s %s' % (file, call)]
if index is not None:
i = lnum - index
for line in lines:
num = '%5d ' % i
rows.append(num + line.rstrip())
i += 1
done, dump = {}, []
for name, where, value in vars:
if name in done:
continue
done[name] = 1
if value is not __UNDEF__:
if where == 'global':
name = 'global ' + name
elif where != 'local':
name = where + name.split('.')[-1]
dump.append('%s = %s' % (name, pydoc.text.repr(value)))
else:
dump.append(name + ' undefined')
rows.append('\n'.join(dump))
frames.append('\n%s\n' % '\n'.join(rows))
exception = ['%s: %s' % (str(etype), str(evalue))]
for name in dir(evalue):
value = pydoc.text.repr(getattr(evalue, name))
exception.append('\n%s%s = %s' % (' ' * 4, name, value))
return head + ''.join(frames) + ''.join(exception) + '''
The above is a description of an error in a Python program. Here is
the original traceback:
%s
''' % ''.join(traceback.format_exception(etype, evalue, etb))
class Hook:
"""A hook to replace sys.excepthook"""
def __init__(self, logdir=None, context=5, file=None):
self.logdir = logdir # log tracebacks to files if not None
self.context = context # number of source code lines per frame
self.file = file or sys.stdout # place to send the output
def __call__(self, etype, evalue, etb):
self.handle((etype, evalue, etb))
def handle(self, info=None):
info = info or sys.exc_info()
formatter = text
try:
doc = formatter(info, self.context)
except: # just in case something goes wrong
doc = ''.join(traceback.format_exception(*info))
self.file.write(doc + '\n')
if self.logdir is not None:
suffix = '.txt'
(fd, path) = tempfile.mkstemp(suffix=suffix, dir=self.logdir)
try:
with os.fdopen(fd, 'w') as file:
file.write(doc)
msg = '%s contains the description of this error.' % path
except:
msg = 'Tried to save traceback to %s, but failed.' % path
self.file.write(msg + '\n')
try:
self.file.flush()
except:
pass
handler = Hook().handle
def enable(logdir=None, context=5):
"""Install an exception handler that sends verbose tracebacks to STDOUT."""
sys.excepthook = Hook(logdir=logdir, context=context)
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