"""Extract, format and print information about Python stack traces."""

import linecache

import sys

import types

__all__ = ['extract_stack', 'extract_tb', 'format_exception',

           'format_exception_only', 'format_list', 'format_stack',

           'format_tb', 'print_exc', 'format_exc', 'print_exception',

           'print_last', 'print_stack', 'print_tb', 'tb_lineno']

def _print(file, str='', terminator='\n'):

    file.write(str+terminator)

def print_list(extracted_list, file=None):

    """Print the list of tuples as returned by extract_tb() or

    extract_stack() as a formatted stack trace to the given file."""

    if file is None:

        file = sys.stderr

    for filename, lineno, name, line in extracted_list:

        _print(file,

               '  File "%s", line %d, in %s' % (filename,lineno,name))

        if line:

            _print(file, '    %s' % line.strip())

def format_list(extracted_list):

    """Format a list of traceback entry tuples for printing.

    Given a list of tuples as returned by extract_tb() or

    extract_stack(), return a list of strings ready for printing.

    Each string in the resulting list corresponds to the item with the

    same index in the argument list.  Each string ends in a newline;

    the strings may contain internal newlines as well, for those items

    whose source text line is not None.

    """

    list = []

    for filename, lineno, name, line in extracted_list:

        item = '  File "%s", line %d, in %s\n' % (filename,lineno,name)

        if line:

            item = item + '    %s\n' % line.strip()

        list.append(item)

    return list

def print_tb(tb, limit=None, file=None):

    """Print up to 'limit' stack trace entries from the traceback 'tb'.

    If 'limit' is omitted or None, all entries are printed.  If 'file'

    is omitted or None, the output goes to sys.stderr; otherwise

    'file' should be an open file or file-like object with a write()

    method.

    """

    if file is None:

        file = sys.stderr

    if limit is None:

        if hasattr(sys, 'tracebacklimit'):

            limit = sys.tracebacklimit

    n = 0

    while tb is not None and (limit is None or n < limit):

        f = tb.tb_frame

        lineno = tb.tb_lineno

        co = f.f_code

        filename = co.co_filename

        name = co.co_name

        _print(file,

               '  File "%s", line %d, in %s' % (filename,lineno,name))

        linecache.checkcache(filename)

        line = linecache.getline(filename, lineno, f.f_globals)

        if line: _print(file, '    ' + line.strip())

        tb = tb.tb_next

        n = n+1

def format_tb(tb, limit = None):

    """A shorthand for 'format_list(extract_stack(f, limit))."""

    return format_list(extract_tb(tb, limit))

def extract_tb(tb, limit = None):

    """Return list of up to limit pre-processed entries from traceback.

    This is useful for alternate formatting of stack traces.  If

    'limit' is omitted or None, all entries are extracted.  A

    pre-processed stack trace entry is a quadruple (filename, line

    number, function name, text) representing the information that is

    usually printed for a stack trace.  The text is a string with

    leading and trailing whitespace stripped; if the source is not

    available it is None.

    """

    if limit is None:

        if hasattr(sys, 'tracebacklimit'):

            limit = sys.tracebacklimit

    list = []

    n = 0

    while tb is not None and (limit is None or n < limit):

        f = tb.tb_frame

        lineno = tb.tb_lineno

        co = f.f_code

        filename = co.co_filename

        name = co.co_name

        linecache.checkcache(filename)

        line = linecache.getline(filename, lineno, f.f_globals)

        if line: line = line.strip()

        else: line = None

        list.append((filename, lineno, name, line))

        tb = tb.tb_next

        n = n+1

    return list

def print_exception(etype, value, tb, limit=None, file=None):

    """Print exception up to 'limit' stack trace entries from 'tb' to 'file'.

    This differs from print_tb() in the following ways: (1) if

    traceback is not None, it prints a header "Traceback (most recent

    call last):"; (2) it prints the exception type and value after the

    stack trace; (3) if type is SyntaxError and value has the

    appropriate format, it prints the line where the syntax error

    occurred with a caret on the next line indicating the approximate

    position of the error.

    """

    if file is None:

        file = sys.stderr

    if tb:

        _print(file, 'Traceback (most recent call last):')

        print_tb(tb, limit, file)

    lines = format_exception_only(etype, value)

    for line in lines[:-1]:

        _print(file, line, ' ')

    _print(file, lines[-1], '')

def format_exception(etype, value, tb, limit = None):

    """Format a stack trace and the exception information.

    The arguments have the same meaning as the corresponding arguments

    to print_exception().  The return value is a list of strings, each

    ending in a newline and some containing internal newlines.  When

    these lines are concatenated and printed, exactly the same text is

    printed as does print_exception().

    """

    if tb:

        list = ['Traceback (most recent call last):\n']

        list = list + format_tb(tb, limit)

    else:

        list = []

    list = list + format_exception_only(etype, value)

    return list

def format_exception_only(etype, value):

    """Format the exception part of a traceback.

    The arguments are the exception type and value such as given by

    sys.last_type and sys.last_value. The return value is a list of

    strings, each ending in a newline.

    Normally, the list contains a single string; however, for

    SyntaxError exceptions, it contains several lines that (when

    printed) display detailed information about where the syntax

    error occurred.

    The message indicating which exception occurred is always the last

    string in the list.

    """

    # An instance should not have a meaningful value parameter, but

    # sometimes does, particularly for string exceptions, such as

    # >>> raise string1, string2  # deprecated

    #

    # Clear these out first because issubtype(string1, SyntaxError)

    # would throw another exception and mask the original problem.

    if (isinstance(etype, BaseException) or

        isinstance(etype, types.InstanceType) or

        etype is None or type(etype) is str):

        return [_format_final_exc_line(etype, value)]

    stype = etype.__name__

    if not issubclass(etype, SyntaxError):

        return [_format_final_exc_line(stype, value)]

    # It was a syntax error; show exactly where the problem was found.

    lines = []

    try:

        msg, (filename, lineno, offset, badline) = value

    except Exception:

        pass

    else:

        filename = filename or "<string>"

        lines.append('  File "%s", line %d\n' % (filename, lineno))

        if badline is not None:

            lines.append('    %s\n' % badline.strip())

            if offset is not None:

                caretspace = badline[:offset].lstrip()

                # non-space whitespace (likes tabs) must be kept for alignment

                caretspace = ((c.isspace() and c or ' ') for c in caretspace)

                # only three spaces to account for offset1 == pos 0

                lines.append('   %s^\n' % ''.join(caretspace))

            value = msg

    lines.append(_format_final_exc_line(stype, value))

    return lines

def _format_final_exc_line(etype, value):

    """Return a list of a single line -- normal case for format_exception_only"""

    valuestr = _some_str(value)

    if value is None or not valuestr:

        line = "%s\n" % etype

    else:

        line = "%s: %s\n" % (etype, valuestr)

    return line

def _some_str(value):

    try:

        return str(value)

    except:

        return '<unprintable %s object>' % type(value).__name__

def print_exc(limit=None, file=None):

    """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'.

    (In fact, it uses sys.exc_info() to retrieve the same information

    in a thread-safe way.)"""

    if file is None:

        file = sys.stderr

    try:

        etype, value, tb = sys.exc_info()

        print_exception(etype, value, tb, limit, file)

    finally:

        etype = value = tb = None

def format_exc(limit=None):

    """Like print_exc() but return a string."""

    try:

        etype, value, tb = sys.exc_info()

        return ''.join(format_exception(etype, value, tb, limit))

    finally:

        etype = value = tb = None

def print_last(limit=None, file=None):

    """This is a shorthand for 'print_exception(sys.last_type,

    sys.last_value, sys.last_traceback, limit, file)'."""

    if file is None:

        file = sys.stderr

    print_exception(sys.last_type, sys.last_value, sys.last_traceback,

                    limit, file)

def print_stack(f=None, limit=None, file=None):

    """Print a stack trace from its invocation point.

    The optional 'f' argument can be used to specify an alternate

    stack frame at which to start. The optional 'limit' and 'file'

    arguments have the same meaning as for print_exception().

    """

    if f is None:

        try:

            raise ZeroDivisionError

        except ZeroDivisionError:

            f = sys.exc_info()[2].tb_frame.f_back

    print_list(extract_stack(f, limit), file)

def format_stack(f=None, limit=None):

    """Shorthand for 'format_list(extract_stack(f, limit))'."""

    if f is None:

        try:

            raise ZeroDivisionError

        except ZeroDivisionError:

            f = sys.exc_info()[2].tb_frame.f_back

    return format_list(extract_stack(f, limit))

def extract_stack(f=None, limit = None):

    """Extract the raw traceback from the current stack frame.

    The return value has the same format as for extract_tb().  The

    optional 'f' and 'limit' arguments have the same meaning as for

    print_stack().  Each item in the list is a quadruple (filename,

    line number, function name, text), and the entries are in order

    from oldest to newest stack frame.

    """

    if f is None:

        try:

            raise ZeroDivisionError

        except ZeroDivisionError:

            f = sys.exc_info()[2].tb_frame.f_back

    if limit is None:

        if hasattr(sys, 'tracebacklimit'):

            limit = sys.tracebacklimit

    list = []

    n = 0

    while f is not None and (limit is None or n < limit):

        lineno = f.f_lineno

        co = f.f_code

        filename = co.co_filename

        name = co.co_name

        linecache.checkcache(filename)

        line = linecache.getline(filename, lineno, f.f_globals)

        if line: line = line.strip()

        else: line = None

        list.append((filename, lineno, name, line))

        f = f.f_back

        n = n+1

    list.reverse()

    return list

def tb_lineno(tb):

    """Calculate correct line number of traceback given in tb.

    Obsolete in 2.3.

    """

    return tb.tb_lineno