cgi.py

#! /usr/local/bin/python

# NOTE: the above "/usr/local/bin/python" is NOT a mistake. It is
# intentionally NOT "/usr/bin/env python". On many systems
# (e.g. Solaris), /usr/local/bin is not in $PATH as passed to CGI
# scripts, and /usr/local/bin is the default directory where Python is
# installed, so /usr/bin/env would be unable to find python. Granted,
# binary installations by Linux vendors often install Python in
# /usr/bin. So let those vendors patch cgi.py to match their choice
# of installation.

"""Support module for CGI (Common Gateway Interface) scripts.

This module defines a number of utilities for use by CGI scripts
written in Python.
"""

# History
# -------
#
# Michael McLay started this module. Steve Majewski changed the
# interface to SvFormContentDict and FormContentDict. The multipart
# parsing was inspired by code submitted by Andreas Paepcke. Guido van
# Rossum rewrote, reformatted and documented the module and is currently
# responsible for its maintenance.
#

# Imports
# =======

fromioimportStringIO, BytesIO, TextIOWrapper
importsys
importos
importurllib.parse
fromemail.parserimportFeedParser
fromwarningsimportwarn
importhtml
importlocale
importtempfile

__all__= [
"MiniFieldStorage",
"FieldStorage",
"parse",
"parse_qs",
"parse_qsl",
"parse_multipart",
"parse_header",
"print_exception",
"print_environ",
"print_form",
"print_directory",
"print_arguments",
"print_environ_usage",
"escape",
]

# Logging support
# ===============

logfile=""# Filename to log to, if not empty
logfp=None# File object to log to, if not None


definitlog(*allargs):
"""Write a log message, if there is a log file.

 Even though this function is called initlog(), you should always
 use log(); log is a variable that is set either to initlog
 (initially), to dolog (once the log file has been opened), or to
 nolog (when logging is disabled).

 The first argument is a format string; the remaining arguments (if
 any) are arguments to the % operator, so e.g.
 log("%s: %s", "a", "b")
 will write "a: b" to the log file, followed by a newline.

 If the global logfp is not None, it should be a file object to
 which log data is written.

 If the global logfp is None, the global logfile may be a string
 giving a filename to open, in append mode. This file should be
 world writable!!! If the file can't be opened, logging is
 silently disabled (since there is no safe place where we could
 send an error message).

 """
globallog, logfile, logfp
iflogfileandnotlogfp:
try:
logfp=open(logfile, "a")
exceptIOError:
pass
ifnotlogfp:
log=nolog
else:
log=dolog
log(*allargs)


defdolog(fmt, *args):
"""Write a log message to the log file. See initlog() for docs."""
logfp.write(fmt%args+"\n")


defnolog(*allargs):
"""Dummy function, assigned to log when logging is disabled."""
pass


defcloselog():
"""Close the log file."""
globallog, logfile, logfp
logfile=""
iflogfp:
logfp.close()
logfp=None
log=initlog


log=initlog# The current logging function


# Parsing functions
# =================

# Maximum input we will accept when REQUEST_METHOD is POST
# 0 ==> unlimited input
maxlen=0


defparse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
"""Parse a query in the environment or from a file (default stdin)

 Arguments, all optional:

 fp : file pointer; default: sys.stdin.buffer

 environ : environment dictionary; default: os.environ

 keep_blank_values: flag indicating whether blank values in
 percent-encoded forms should be treated as blank strings.
 A true value indicates that blanks should be retained as
 blank strings. The default false value indicates that
 blank values are to be ignored and treated as if they were
 not included.

 strict_parsing: flag indicating what to do with parsing errors.
 If false (the default), errors are silently ignored.
 If true, errors raise a ValueError exception.
 """
iffpisNone:
fp=sys.stdin

# field keys and values (except for files) are returned as strings
# an encoding is required to decode the bytes read from self.fp
ifhasattr(fp, "encoding"):
encoding=fp.encoding
else:
encoding="latin-1"

# fp.read() must return bytes
ifisinstance(fp, TextIOWrapper):
fp=fp.buffer

ifnot"REQUEST_METHOD"inenviron:
environ["REQUEST_METHOD"] ="GET"# For testing stand-alone
ifenviron["REQUEST_METHOD"] =="POST":
ctype, pdict=parse_header(environ["CONTENT_TYPE"])
ifctype=="multipart/form-data":
returnparse_multipart(fp, pdict)
elifctype=="application/x-www-form-urlencoded":
clength=int(environ["CONTENT_LENGTH"])
ifmaxlenandclength>maxlen:
raiseValueError("Maximum content length exceeded")
qs=fp.read(clength).decode(encoding)
else:
qs=""# Unknown content-type
if"QUERY_STRING"inenviron:
ifqs:
qs=qs+"&"
qs=qs+environ["QUERY_STRING"]
elifsys.argv[1:]:
ifqs:
qs=qs+"&"
qs=qs+sys.argv[1]
environ["QUERY_STRING"] =qs# XXX Shouldn't, really
elif"QUERY_STRING"inenviron:
qs=environ["QUERY_STRING"]
else:
ifsys.argv[1:]:
qs=sys.argv[1]
else:
qs=""
environ["QUERY_STRING"] =qs# XXX Shouldn't, really
returnurllib.parse.parse_qs(qs, keep_blank_values, strict_parsing, encoding=encoding)


# parse query string function called from urlparse,
# this is done in order to maintain backward compatiblity.


defparse_qs(qs, keep_blank_values=0, strict_parsing=0):
"""Parse a query given as a string argument."""
warn("cgi.parse_qs is deprecated, use urllib.parse.parse_qs instead", DeprecationWarning, 2)
returnurllib.parse.parse_qs(qs, keep_blank_values, strict_parsing)


defparse_qsl(qs, keep_blank_values=0, strict_parsing=0):
"""Parse a query given as a string argument."""
warn("cgi.parse_qsl is deprecated, use urllib.parse.parse_qsl instead", DeprecationWarning, 2)
returnurllib.parse.parse_qsl(qs, keep_blank_values, strict_parsing)


defparse_multipart(fp, pdict):
"""Parse multipart input.

 Arguments:
 fp : input file
 pdict: dictionary containing other parameters of content-type header

 Returns a dictionary just like parse_qs(): keys are the field names, each
 value is a list of values for that field. This is easy to use but not
 much good if you are expecting megabytes to be uploaded -- in that case,
 use the FieldStorage class instead which is much more flexible. Note
 that content-type is the raw, unparsed contents of the content-type
 header.

 XXX This does not parse nested multipart parts -- use FieldStorage for
 that.

 XXX This should really be subsumed by FieldStorage altogether -- no
 point in having two implementations of the same parsing algorithm.
 Also, FieldStorage protects itself better against certain DoS attacks
 by limiting the size of the data read in one chunk. The API here
 does not support that kind of protection. This also affects parse()
 since it can call parse_multipart().

 """
importhttp.client

boundary=b""
if"boundary"inpdict:
boundary=pdict["boundary"]
ifnotvalid_boundary(boundary):
raiseValueError("Invalid boundary in multipart form: %r"% (boundary,))

nextpart=b"--"+boundary
lastpart=b"--"+boundary+b"--"
partdict= {}
terminator=b""

whileterminator!=lastpart:
bytes=-1
data=None
ifterminator:
# At start of next part. Read headers first.
headers=http.client.parse_headers(fp)
clength=headers.get("content-length")
ifclength:
try:
bytes=int(clength)
exceptValueError:
pass
ifbytes>0:
ifmaxlenandbytes>maxlen:
raiseValueError("Maximum content length exceeded")
data=fp.read(bytes)
else:
data=b""
# Read lines until end of part.
lines= []
while1:
line=fp.readline()
ifnotline:
terminator=lastpart# End outer loop
break
ifline.startswith(b"--"):
terminator=line.rstrip()
ifterminatorin (nextpart, lastpart):
break
lines.append(line)
# Done with part.
ifdataisNone:
continue
ifbytes<0:
iflines:
# Strip final line terminator
line=lines[-1]
ifline[-2:] ==b"\r\n":
line=line[:-2]
elifline[-1:] ==b"\n":
line=line[:-1]
lines[-1] =line
data=b"".join(lines)
line=headers["content-disposition"]
ifnotline:
continue
key, params=parse_header(line)
ifkey!="form-data":
continue
if"name"inparams:
name=params["name"]
else:
continue
ifnameinpartdict:
partdict[name].append(data)
else:
partdict[name] = [data]

returnpartdict


def_parseparam(s):
whiles[:1] ==";":
s=s[1:]
end=s.find(";")
whileend>0and (s.count('"', 0, end) -s.count('\\"', 0, end)) %2:
end=s.find(";", end+1)
ifend<0:
end=len(s)
f=s[:end]
yieldf.strip()
s=s[end:]


defparse_header(line):
"""Parse a Content-type like header.

 Return the main content-type and a dictionary of options.

 """
parts=_parseparam(";"+line)
key=parts.__next__()
pdict= {}
forpinparts:
i=p.find("=")
ifi>=0:
name=p[:i].strip().lower()
value=p[i+1 :].strip()
iflen(value) >=2andvalue[0] ==value[-1] =='"':
value=value[1:-1]
value=value.replace("\\\\", "\\").replace('\\"', '"')
pdict[name] =value
returnkey, pdict


# Classes for field storage
# =========================


classMiniFieldStorage:

"""Like FieldStorage, for use when no file uploads are possible."""

# Dummy attributes
filename=None
list=None
type=None
file=None
type_options= {}
disposition=None
disposition_options= {}
headers= {}

def__init__(self, name, value):
"""Constructor from field name and value."""
self.name=name
self.value=value
# self.file = StringIO(value)

def__repr__(self):
"""Return printable representation."""
return"MiniFieldStorage(%r, %r)"% (self.name, self.value)


classFieldStorage:

"""Store a sequence of fields, reading multipart/form-data.

 This class provides naming, typing, files stored on disk, and
 more. At the top level, it is accessible like a dictionary, whose
 keys are the field names. (Note: None can occur as a field name.)
 The items are either a Python list (if there's multiple values) or
 another FieldStorage or MiniFieldStorage object. If it's a single
 object, it has the following attributes:

 name: the field name, if specified; otherwise None

 filename: the filename, if specified; otherwise None; this is the
 client side filename, *not* the file name on which it is
 stored (that's a temporary file you don't deal with)

 value: the value as a *string*; for file uploads, this
 transparently reads the file every time you request the value
 and returns *bytes*

 file: the file(-like) object from which you can read the data *as
 bytes* ; None if the data is stored a simple string

 type: the content-type, or None if not specified

 type_options: dictionary of options specified on the content-type
 line

 disposition: content-disposition, or None if not specified

 disposition_options: dictionary of corresponding options

 headers: a dictionary(-like) object (sometimes email.message.Message or a
 subclass thereof) containing *all* headers

 The class is subclassable, mostly for the purpose of overriding
 the make_file() method, which is called internally to come up with
 a file open for reading and writing. This makes it possible to
 override the default choice of storing all files in a temporary
 directory and unlinking them as soon as they have been opened.

 """

def__init__(
self,
fp=None,
headers=None,
outerboundary=b"",
environ=os.environ,
keep_blank_values=0,
strict_parsing=0,
limit=None,
encoding="utf-8",
errors="replace",
 ):
"""Constructor. Read multipart/* until last part.

 Arguments, all optional:

 fp : file pointer; default: sys.stdin.buffer
 (not used when the request method is GET)
 Can be :
 1. a TextIOWrapper object
 2. an object whose read() and readline() methods return bytes

 headers : header dictionary-like object; default:
 taken from environ as per CGI spec

 outerboundary : terminating multipart boundary
 (for internal use only)

 environ : environment dictionary; default: os.environ

 keep_blank_values: flag indicating whether blank values in
 percent-encoded forms should be treated as blank strings.
 A true value indicates that blanks should be retained as
 blank strings. The default false value indicates that
 blank values are to be ignored and treated as if they were
 not included.

 strict_parsing: flag indicating what to do with parsing errors.
 If false (the default), errors are silently ignored.
 If true, errors raise a ValueError exception.

 limit : used internally to read parts of multipart/form-data forms,
 to exit from the reading loop when reached. It is the difference
 between the form content-length and the number of bytes already
 read

 encoding, errors : the encoding and error handler used to decode the
 binary stream to strings. Must be the same as the charset defined
 for the page sending the form (content-type : meta http-equiv or
 header)

 """
method="GET"
self.keep_blank_values=keep_blank_values
self.strict_parsing=strict_parsing
if"REQUEST_METHOD"inenviron:
method=environ["REQUEST_METHOD"].upper()
self.qs_on_post=None
ifmethod=="GET"ormethod=="HEAD":
if"QUERY_STRING"inenviron:
qs=environ["QUERY_STRING"]
elifsys.argv[1:]:
qs=sys.argv[1]
else:
qs=""
qs=qs.encode(locale.getpreferredencoding(), "surrogateescape")
fp=BytesIO(qs)
ifheadersisNone:
headers= {"content-type": "application/x-www-form-urlencoded"}
ifheadersisNone:
headers= {}
ifmethod=="POST":
# Set default content-type for POST to what's traditional
headers["content-type"] ="application/x-www-form-urlencoded"
if"CONTENT_TYPE"inenviron:
headers["content-type"] =environ["CONTENT_TYPE"]
if"QUERY_STRING"inenviron:
self.qs_on_post=environ["QUERY_STRING"]
if"CONTENT_LENGTH"inenviron:
headers["content-length"] =environ["CONTENT_LENGTH"]
iffpisNone:
self.fp=sys.stdin.buffer
# self.fp.read() must return bytes
elifisinstance(fp, TextIOWrapper):
self.fp=fp.buffer
else:
self.fp=fp

self.encoding=encoding
self.errors=errors

self.headers=headers
ifnotisinstance(outerboundary, bytes):
raiseTypeError("outerboundary must be bytes, not %s"%type(outerboundary).__name__)
self.outerboundary=outerboundary

self.bytes_read=0
self.limit=limit

# Process content-disposition header
cdisp, pdict="", {}
if"content-disposition"inself.headers:
cdisp, pdict=parse_header(self.headers["content-disposition"])
self.disposition=cdisp
self.disposition_options=pdict
self.name=None
if"name"inpdict:
self.name=pdict["name"]
self.filename=None
if"filename"inpdict:
self.filename=pdict["filename"]
self._binary_file=self.filenameisnotNone

# Process content-type header
#
# Honor any existing content-type header. But if there is no
# content-type header, use some sensible defaults. Assume
# outerboundary is "" at the outer level, but something non-false
# inside a multi-part. The default for an inner part is text/plain,
# but for an outer part it should be urlencoded. This should catch
# bogus clients which erroneously forget to include a content-type
# header.
#
# See below for what we do if there does exist a content-type header,
# but it happens to be something we don't understand.
if"content-type"inself.headers:
ctype, pdict=parse_header(self.headers["content-type"])
elifself.outerboundaryormethod!="POST":
ctype, pdict="text/plain", {}
else:
ctype, pdict="application/x-www-form-urlencoded", {}
self.type=ctype
self.type_options=pdict
if"boundary"inpdict:
self.innerboundary=pdict["boundary"].encode(self.encoding)
else:
self.innerboundary=b""

clen=-1
if"content-length"inself.headers:
try:
clen=int(self.headers["content-length"])
exceptValueError:
pass
ifmaxlenandclen>maxlen:
raiseValueError("Maximum content length exceeded")
self.length=clen
ifself.limitisNoneandclen:
self.limit=clen

self.list=self.file=None
self.done=0
ifctype=="application/x-www-form-urlencoded":
self.read_urlencoded()
elifctype[:10] =="multipart/":
self.read_multi(environ, keep_blank_values, strict_parsing)
else:
self.read_single()

def__repr__(self):
"""Return a printable representation."""
return"FieldStorage(%r, %r, %r)"% (self.name, self.filename, self.value)

def__iter__(self):
returniter(self.keys())

def__getattr__(self, name):
ifname!="value":
raiseAttributeError(name)
ifself.file:
self.file.seek(0)
value=self.file.read()
self.file.seek(0)
elifself.listisnotNone:
value=self.list
else:
value=None
returnvalue

def__getitem__(self, key):
"""Dictionary style indexing."""
ifself.listisNone:
raiseTypeError("not indexable")
found= []
foriteminself.list:
ifitem.name==key:
found.append(item)
ifnotfound:
raiseKeyError(key)
iflen(found) ==1:
returnfound[0]
else:
returnfound

defgetvalue(self, key, default=None):
"""Dictionary style get() method, including 'value' lookup."""
ifkeyinself:
value=self[key]
ifisinstance(value, list):
return [x.valueforxinvalue]
else:
returnvalue.value
else:
returndefault

defgetfirst(self, key, default=None):
"""Return the first value received."""
ifkeyinself:
value=self[key]
ifisinstance(value, list):
returnvalue[0].value
else:
returnvalue.value
else:
returndefault

defgetlist(self, key):
"""Return list of received values."""
ifkeyinself:
value=self[key]
ifisinstance(value, list):
return [x.valueforxinvalue]
else:
return [value.value]
else:
return []

defkeys(self):
"""Dictionary style keys() method."""
ifself.listisNone:
raiseTypeError("not indexable")
returnlist(set(item.nameforiteminself.list))

def__contains__(self, key):
"""Dictionary style __contains__ method."""
ifself.listisNone:
raiseTypeError("not indexable")
returnany(item.name==keyforiteminself.list)

def__len__(self):
"""Dictionary style len(x) support."""
returnlen(self.keys())

def__nonzero__(self):
returnbool(self.list)

defread_urlencoded(self):
"""Internal: read data in query string format."""
qs=self.fp.read(self.length)
ifnotisinstance(qs, bytes):
raiseValueError("%s should return bytes, got %s"% (self.fp, type(qs).__name__))
qs=qs.decode(self.encoding, self.errors)
ifself.qs_on_post:
qs+="&"+self.qs_on_post
self.list= []
query=urllib.parse.parse_qsl(
qs,
self.keep_blank_values,
self.strict_parsing,
encoding=self.encoding,
errors=self.errors,
 )
forkey, valueinquery:
self.list.append(MiniFieldStorage(key, value))
self.skip_lines()

FieldStorageClass=None

defread_multi(self, environ, keep_blank_values, strict_parsing):
"""Internal: read a part that is itself multipart."""
ib=self.innerboundary
ifnotvalid_boundary(ib):
raiseValueError("Invalid boundary in multipart form: %r"% (ib,))
self.list= []
ifself.qs_on_post:
query=urllib.parse.parse_qsl(
self.qs_on_post,
self.keep_blank_values,
self.strict_parsing,
encoding=self.encoding,
errors=self.errors,
 )
forkey, valueinquery:
self.list.append(MiniFieldStorage(key, value))
FieldStorageClass=None

klass=self.FieldStorageClassorself.__class__
first_line=self.fp.readline() # bytes
ifnotisinstance(first_line, bytes):
raiseValueError(
"%s should return bytes, got %s"% (self.fp, type(first_line).__name__)
 )
self.bytes_read+=len(first_line)
# first line holds boundary ; ignore it, or check that
# b"--" + ib == first_line.strip() ?
whileTrue:
parser=FeedParser()
hdr_text=b""
whileTrue:
data=self.fp.readline()
hdr_text+=data
ifnotdata.strip():
break
ifnothdr_text:
break
# parser takes strings, not bytes
self.bytes_read+=len(hdr_text)
parser.feed(hdr_text.decode(self.encoding, self.errors))
headers=parser.close()
part=klass(
self.fp,
headers,
ib,
environ,
keep_blank_values,
strict_parsing,
self.limit-self.bytes_read,
self.encoding,
self.errors,
 )
self.bytes_read+=part.bytes_read
self.list.append(part)
ifpart.doneorself.bytes_read>=self.length>0:
break
self.skip_lines()

defread_single(self):
"""Internal: read an atomic part."""
ifself.length>=0:
self.read_binary()
self.skip_lines()
else:
self.read_lines()
self.file.seek(0)

bufsize=8*1024# I/O buffering size for copy to file

defread_binary(self):
"""Internal: read binary data."""
self.file=self.make_file()
todo=self.length
iftodo>=0:
whiletodo>0:
data=self.fp.read(min(todo, self.bufsize)) # bytes
ifnotisinstance(data, bytes):
raiseValueError(
"%s should return bytes, got %s"% (self.fp, type(data).__name__)
 )
self.bytes_read+=len(data)
ifnotdata:
self.done=-1
break
self.file.write(data)
todo=todo-len(data)

defread_lines(self):
"""Internal: read lines until EOF or outerboundary."""
ifself._binary_file:
self.file=self.__file=BytesIO() # store data as bytes for files
else:
self.file=self.__file=StringIO() # as strings for other fields
ifself.outerboundary:
self.read_lines_to_outerboundary()
else:
self.read_lines_to_eof()

def__write(self, line):
"""line is always bytes, not string"""
ifself.__fileisnotNone:
ifself.__file.tell() +len(line) >1000:
self.file=self.make_file()
data=self.__file.getvalue()
self.file.write(data)
self.__file=None
ifself._binary_file:
# keep bytes
self.file.write(line)
else:
# decode to string
self.file.write(line.decode(self.encoding, self.errors))

defread_lines_to_eof(self):
"""Internal: read lines until EOF."""
while1:
line=self.fp.readline(1<<16) # bytes
self.bytes_read+=len(line)
ifnotline:
self.done=-1
break
self.__write(line)

defread_lines_to_outerboundary(self):
"""Internal: read lines until outerboundary.
 Data is read as bytes: boundaries and line ends must be converted
 to bytes for comparisons.
 """
next_boundary=b"--"+self.outerboundary
last_boundary=next_boundary+b"--"
delim=b""
last_line_lfend=True
_read=0
while1:
if_read>=self.limit:
break
line=self.fp.readline(1<<16) # bytes
self.bytes_read+=len(line)
_read+=len(line)
ifnotline:
self.done=-1
break
ifdelim==b"\r":
line=delim+line
delim=b""
ifline.startswith(b"--") andlast_line_lfend:
strippedline=line.rstrip()
ifstrippedline==next_boundary:
break
ifstrippedline==last_boundary:
self.done=1
break
odelim=delim
ifline.endswith(b"\r\n"):
delim=b"\r\n"
line=line[:-2]
last_line_lfend=True
elifline.endswith(b"\n"):
delim=b"\n"
line=line[:-1]
last_line_lfend=True
elifline.endswith(b"\r"):
# We may interrupt \r\n sequences if they span the 2**16
# byte boundary
delim=b"\r"
line=line[:-1]
last_line_lfend=False
else:
delim=b""
last_line_lfend=False
self.__write(odelim+line)

defskip_lines(self):
"""Internal: skip lines until outer boundary if defined."""
ifnotself.outerboundaryorself.done:
return
next_boundary=b"--"+self.outerboundary
last_boundary=next_boundary+b"--"
last_line_lfend=True
whileTrue:
line=self.fp.readline(1<<16)
self.bytes_read+=len(line)
ifnotline:
self.done=-1
break
ifline.endswith(b"--") andlast_line_lfend:
strippedline=line.strip()
ifstrippedline==next_boundary:
break
ifstrippedline==last_boundary:
self.done=1
break
last_line_lfend=line.endswith(b"\n")

defmake_file(self):
"""Overridable: return a readable & writable file.

 The file will be used as follows:
 - data is written to it
 - seek(0)
 - data is read from it

 The file is opened in binary mode for files, in text mode
 for other fields

 This version opens a temporary file for reading and writing,
 and immediately deletes (unlinks) it. The trick (on Unix!) is
 that the file can still be used, but it can't be opened by
 another process, and it will automatically be deleted when it
 is closed or when the current process terminates.

 If you want a more permanent file, you derive a class which
 overrides this method. If you want a visible temporary file
 that is nevertheless automatically deleted when the script
 terminates, try defining a __del__ method in a derived class
 which unlinks the temporary files you have created.

 """
ifself._binary_file:
returntempfile.TemporaryFile("wb+")
else:
returntempfile.TemporaryFile("w+", encoding=self.encoding, newline="\n")


# Test/debug code
# ===============


deftest(environ=os.environ):
"""Robust test CGI script, usable as main program.

 Write minimal HTTP headers and dump all information provided to
 the script in HTML form.

 """
print("Content-type: text/html")
print()
# sys.stderr = sys.stdout
try:
form=FieldStorage() # Replace with other classes to test those
print_directory()
print_arguments()
print_form(form)
print_environ(environ)
print_environ_usage()

deff():
exec("testing print_exception() -- <I>italics?</I>")

defg(f=f):
f()

print("<H3>What follows is a test, not an actual exception:</H3>")
g()
except:
print_exception()

print("<H1>Second try with a small maxlen...</H1>")

globalmaxlen
maxlen=50
try:
form=FieldStorage() # Replace with other classes to test those
print_directory()
print_arguments()
print_form(form)
print_environ(environ)
except:
print_exception()


defprint_exception(type=None, value=None, tb=None, limit=None):
iftypeisNone:
type, value, tb=sys.exc_info()
importtraceback

print()
print("<H3>Traceback (most recent call last):</H3>")
list=traceback.format_tb(tb, limit) +traceback.format_exception_only(type, value)
print(
"<PRE>%s<B>%s</B></PRE>"
% (
html.escape("".join(list[:-1])),
html.escape(list[-1]),
 )
 )
deltb


defprint_environ(environ=os.environ):
"""Dump the shell environment as HTML."""
keys=sorted(environ.keys())
print()
print("<H3>Shell Environment:</H3>")
print("<DL>")
forkeyinkeys:
print("<DT>", html.escape(key), "<DD>", html.escape(environ[key]))
print("</DL>")
print()


defprint_form(form):
"""Dump the contents of a form as HTML."""
keys=sorted(form.keys())
print()
print("<H3>Form Contents:</H3>")
ifnotkeys:
print("<P>No form fields.")
print("<DL>")
forkeyinkeys:
print("<DT>"+html.escape(key) +":", end=" ")
value=form[key]