Preview: cgitb.py
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/usr/lib64/python3.8/cgitb.py
"""More comprehensive traceback formatting for Python scripts.
To enable this module, do:
import cgitb; cgitb.enable()
at the top of your script. The optional arguments to enable() are:
display - if true, tracebacks are displayed in the web browser
logdir - if set, tracebacks are written to files in this directory
context - number of lines of source code to show for each stack frame
format - 'text' or 'html' controls the output format
By default, tracebacks are displayed but not saved, the context is 5 lines
and the output format is 'html' (for backwards compatibility with the
original use of this module)
Alternatively, if you have caught an exception and want cgitb to display it
for you, call cgitb.handler(). The optional argument to handler() is a
3-item tuple (etype, evalue, etb) just like the value of sys.exc_info().
The default handler displays output as HTML.
"""
import inspect
import keyword
import linecache
import os
import pydoc
import sys
import tempfile
import time
import tokenize
import traceback
def reset():
"""Return a string that resets the CGI and browser to a known state."""
return '''<!--: spam
Content-Type: text/html
<body bgcolor="#f0f0f8"><font color="#f0f0f8" size="-5"> -->
<body bgcolor="#f0f0f8"><font color="#f0f0f8" size="-5"> --> -->
</font> </font> </font> </script> </object> </blockquote> </pre>
</table> </table> </table> </table> </table> </font> </font> </font>'''
__UNDEF__ = [] # a special sentinel object
def small(text):
if text:
return '<small>' + text + '</small>'
else:
return ''
def strong(text):
if text:
return '<strong>' + text + '</strong>'
else:
return ''
def grey(text):
if text:
return '<font color="#909090">' + text + '</font>'
else:
return ''
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 type(builtins) is type({}):
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 html(einfo, context=5):
"""Return a nice HTML 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 = '<body bgcolor="#f0f0f8">' + pydoc.html.heading(
'<big><big>%s</big></big>' %
strong(pydoc.html.escape(str(etype))),
'#ffffff', '#6622aa', pyver + '<br>' + date) + '''
<p>A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.</p>'''
indent = '<tt>' + small(' ' * 5) + ' </tt>'
frames = []
records = inspect.getinnerframes(etb, context)
for frame, file, lnum, func, lines, index in records:
if file:
file = os.path.abspath(file)
link = '<a href="file://%s">%s</a>' % (file, pydoc.html.escape(file))
else:
file = link = '?'
args, varargs, varkw, locals = inspect.getargvalues(frame)
call = ''
if func != '?':
call = 'in ' + strong(pydoc.html.escape(func))
if func != "<module>":
call += inspect.formatargvalues(args, varargs, varkw, locals,
formatvalue=lambda value: '=' + pydoc.html.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 = ['<tr><td bgcolor="#d8bbff">%s%s %s</td></tr>' %
('<big> </big>', link, call)]
if index is not None:
i = lnum - index
for line in lines:
num = small(' ' * (5-len(str(i))) + str(i)) + ' '
if i in highlight:
line = '<tt>=>%s%s</tt>' % (num, pydoc.html.preformat(line))
rows.append('<tr><td bgcolor="#ffccee">%s</td></tr>' % line)
else:
line = '<tt> %s%s</tt>' % (num, pydoc.html.preformat(line))
rows.append('<tr><td>%s</td></tr>' % grey(line))
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 in ('global', 'builtin'):
name = ('<em>%s</em> ' % where) + strong(name)
elif where == 'local':
name = strong(name)
else:
name = where + strong(name.split('.')[-1])
dump.append('%s = %s' % (name, pydoc.html.repr(value)))
else:
dump.append(name + ' <em>undefined</em>')
rows.append('<tr><td>%s</td></tr>' % small(grey(', '.join(dump))))
frames.append('''
<table width="100%%" cellspacing=0 cellpadding=0 border=0>
%s</table>''' % '\n'.join(rows))
exception = ['<p>%s: %s' % (strong(pydoc.html.escape(str(etype))),
pydoc.html.escape(str(evalue)))]
for name in dir(evalue):
if name[:1] == '_': continue
value = pydoc.html.repr(getattr(evalue, name))
exception.append('\n<br>%s%s =\n%s' % (indent, name, value))
return head + ''.join(frames) + ''.join(exception) + '''
<!-- The above is a description of an error in a Python program, formatted
for a Web browser because the 'cgitb' module was enabled. In case you
are not reading this in a Web browser, here is the original traceback:
%s
-->
''' % pydoc.html.escape(
''.join(traceback.format_exception(etype, evalue, etb)))
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
if func != "<module>":
call += 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 that shows tracebacks in HTML."""
def __init__(self, display=1, logdir=None, context=5, file=None,
format="html"):
self.display = display # send tracebacks to browser if true
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
self.format = format
def __call__(self, etype, evalue, etb):
self.handle((etype, evalue, etb))
def handle(self, info=None):
info = info or sys.exc_info()
if self.format == "html":
self.file.write(reset())
formatter = (self.format=="html") and html or text
plain = False
try:
doc = formatter(info, self.context)
except: # just in case something goes wrong
doc = ''.join(traceback.format_exception(*info))
plain = True
if self.display:
if plain:
doc = pydoc.html.escape(doc)
self.file.write('<pre>' + doc + '</pre>\n')
else:
self.file.write(doc + '\n')
else:
self.file.write('<p>A problem occurred in a Python script.\n')
if self.logdir is not None:
suffix = ['.txt', '.html'][self.format=="html"]
(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
if self.format == 'html':
self.file.write('<p>%s</p>\n' % msg)
else:
self.file.write(msg + '\n')
try:
self.file.flush()
except: pass
handler = Hook().handle
def enable(display=1, logdir=None, context=5, format="html"):
"""Install an exception handler that formats tracebacks as HTML.
The optional argument 'display' can be set to 0 to suppress sending the
traceback to the browser, and 'logdir' can be set to a directory to cause
tracebacks to be written to files there."""
sys.excepthook = Hook(display=display, logdir=logdir,
context=context, format=format)
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