Question

我们说我有以下多行字符串：

cmd = """
    a = 1 + 1
    b = [
       2 + 2,
       4 + 4,
    ]
    bork bork bork
"""

我希望在特定范围内执行它：

scope = {}
exec( cmd, scope )
print scope[ 'b' ]

命令第6行有SyntaxError，我希望能够向用户报告。我如何获得行号？我试过这个：

try:
    exec( cmd, scope )  # <-- let's say this is on line 123 of the source file
except Exception, err:
    a, b, c = sys.exc_info()
    line_number = c.tb_lineno  # <-- this gets me 123,  not 6
    print "%s at line %d (%s)" % ( a, line_number, b.message )

...但是我得到了exec语句的行号，而不是多行命令中的行号。

更新：事实证明，我为此示例任意选择的异常类型的处理SyntaxError与处理任何其他类型不同。为了澄清，我正在寻找一种能够应对任何异常的解决方案。

Answer 1

对于语法错误，源行号可作为异常对象本身的lineno标志，在您的情况下存储在err中。这特定于语法错误，其中行号是错误的组成部分：

>>> cmd = """
... 1 \ +
... 2 * "
... """
>>> try:
...   exec cmd
... except SyntaxError as err:
...   print err.lineno
... 
2

如果您还要处理其他错误，请添加新的except块except Exception, err，并使用traceback模块计算运行时错误的行号。

import sys
import traceback

class InterpreterError(Exception): pass

def my_exec(cmd, globals=None, locals=None, description='source string'):
    try:
        exec(cmd, globals, locals)
    except SyntaxError as err:
        error_class = err.__class__.__name__
        detail = err.args[0]
        line_number = err.lineno
    except Exception as err:
        error_class = err.__class__.__name__
        detail = err.args[0]
        cl, exc, tb = sys.exc_info()
        line_number = traceback.extract_tb(tb)[-1][1]
    else:
        return
    raise InterpreterError("%s at line %d of %s: %s" % (error_class, line_number, description, detail))

示例：

>>> my_exec("1+1")  # no exception
>>>
>>> my_exec("1+1\nbork")
...
InterpreterError: NameError at line 2 of source string: name 'bork' is not defined
>>>
>>> my_exec("1+1\nbork bork bork")
...
InterpreterError: SyntaxError at line 2 of source string: invalid syntax
>>>
>>> my_exec("1+1\n'''")
...
InterpreterError: SyntaxError at line 2 of source string: EOF while scanning triple-quoted string

如何从Python中的exec或execfile获取错误的行号

1 个答案: