traceback — 异常和栈的回溯

Supporting Functions

# traceback_example.py
import traceback
import sys


def produce_exception(recursion_level=2):
    sys.stdout.flush()
    if recursion_level:
        produce_exception(recursion_level - 1)
    else:
        raise RuntimeError()


def call_function(f, recursion_level=2):
    if recursion_level:
        return call_function(f, recursion_level - 1)
    else:
        return f()

Examining the Stack

# traceback_stacksummary.py
import traceback
import sys

from traceback_example import call_function


def f():
    summary = traceback.StackSummary.extract(
        traceback.walk_stack(None)
    )
    print(''.join(summary.format()))


print('Calling f() directly:')
f()

print()
print('Calling f() from 3 levels deep:')
call_function(f)

# traceback_framesummary.py
import traceback
import sys

from traceback_example import call_function

template = (
    '{fs.filename:<26}:{fs.lineno}:{fs.name}:\n'
    '    {fs.line}'
)


def f():
    summary = traceback.StackSummary.extract(
        traceback.walk_stack(None)
    )
    for fs in summary:
        print(template.format(fs=fs))


print('Calling f() directly:')
f()

print()
print('Calling f() from 3 levels deep:')
call_function(f)

TracebackException

# traceback_tracebackexception.py
import traceback
import sys

from traceback_example import produce_exception

print('with no exception:')
exc_type, exc_value, exc_tb = sys.exc_info()
tbe = traceback.TracebackException(exc_type, exc_value, exc_tb)
print(''.join(tbe.format()))

print('\nwith exception:')
try:
    produce_exception()
except Exception as err:
    exc_type, exc_value, exc_tb = sys.exc_info()
    tbe = traceback.TracebackException(
        exc_type, exc_value, exc_tb,
    )
    print(''.join(tbe.format()))

    print('\nexception only:')
    print(''.join(tbe.format_exception_only()))

Low-level Exception APIs

# traceback_print_exc.py
import traceback
import sys

from traceback_example import produce_exception

print('print_exc() with no exception:')
traceback.print_exc(file=sys.stdout)
print()

try:
    produce_exception()
except Exception as err:
    print('print_exc():')
    traceback.print_exc(file=sys.stdout)
    print()
    print('print_exc(1):')
    traceback.print_exc(limit=1, file=sys.stdout)

# traceback_print_exception.py
import traceback
import sys

from traceback_example import produce_exception

try:
    produce_exception()
except Exception as err:
    print('print_exception():')
    exc_type, exc_value, exc_tb = sys.exc_info()
    traceback.print_exception(exc_type, exc_value, exc_tb)

# traceback_format_exception.py
import traceback
import sys
from pprint import pprint

from traceback_example import produce_exception

try:
    produce_exception()
except Exception as err:
    print('format_exception():')
    exc_type, exc_value, exc_tb = sys.exc_info()
    pprint(
        traceback.format_exception(exc_type, exc_value, exc_tb),
        width=65,
    )

# traceback_extract_tb.py
import traceback
import sys
import os
from traceback_example import produce_exception

template = '{filename:<23}:{linenum}:{funcname}:\n    {source}'

try:
    produce_exception()
except Exception as err:
    print('format_exception():')
    exc_type, exc_value, exc_tb = sys.exc_info()
    for tb_info in traceback.extract_tb(exc_tb):
        filename, linenum, funcname, source = tb_info
        if funcname != '<module>':
            funcname = funcname + '()'
        print(template.format(
            filename=os.path.basename(filename),
            linenum=linenum,
            source=source,
            funcname=funcname)
        )

Low-level Stack APIs

# traceback_print_stack.py
import traceback
import sys

from traceback_example import call_function


def f():
    traceback.print_stack(file=sys.stdout)


print('Calling f() directly:')
f()

print()
print('Calling f() from 3 levels deep:')
call_function(f)

# traceback_format_stack.py
import traceback
import sys
from pprint import pprint

from traceback_example import call_function


def f():
    return traceback.format_stack()


formatted_stack = call_function(f)
pprint(formatted_stack)

# traceback_extract_stack.py
import traceback
import sys
import os

from traceback_example import call_function

template = '{filename:<26}:{linenum}:{funcname}:\n    {source}'


def f():
    return traceback.extract_stack()


stack = call_function(f)
for filename, linenum, funcname, source in stack:
    if funcname != '<module>':
        funcname = funcname + '()'
    print(template.format(
        filename=os.path.basename(filename),
        linenum=linenum,
        source=source,
        funcname=funcname)
    )