Python eval 错误抑制
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Python eval error suppression
提问by lamas
First off, I'm aware of eval's disadvantages and it will be used in an experiment I want to make only.
首先，我知道 eval 的缺点，它将用于我只想做的实验。
I'm creating a script that works just like a Brute-Force algorithm but it won't break passwords but find the solution to a special form of an equation (more details are unnecessary).
我正在创建一个脚本，它的工作原理类似于蛮力算法，但它不会破解密码，但会找到特殊形式的方程的解决方案（不需要更多细节）。
There will be lots of strings filled with (often syntactically incorrect) terms like 1+2)+3
将有很多字符串填充（通常是语法错误的）术语，例如1+2)+3
- Is the only way to get the results of these terms via
eval? - How to make python ignore syntactical errors occurring in
eval? (The program shouldn't terminate)
- 是通过 获得这些术语结果的唯一方法
eval吗？ - 如何让python忽略出现的语法错误
eval？（程序不应终止）
回答by Dominic Rodger
回答by Roberto Rosario
use literal_eval from ast instead and catch ValueError and SyntaxError
改用 ast 中的literal_eval 并捕获ValueError 和SyntaxError
from ast import literal_eval
try:
a = literal_eval('1+2)+3')
except (ValueError, SyntaxError):
pass
回答by Stephan Geue
There are more exceptions possible than SyntaxError only:
可能有比 SyntaxError 更多的异常：
ZeroDivisionError, e.g. for
"1/0"NameError, e.g. for
"franz/3"(with undefinedfranz)TypeError, e.g. for
"[2, 4]/2"
ZeroDivisionError，例如对于
"1/0"NameError，例如 for
"franz/3"(with undefinedfranz)类型错误，例如
"[2, 4]/2"
and even more. So, you may want to catch them all:
甚至更多。因此，您可能想将它们全部捕获：
try:
eval (expr)
except (SyntaxError, NameError, TypeError, ZeroDivisionError):
pass
Actually, virtually allexisting exceptions can be thrown and any havoc can be wreaked by the evaluation of any code unless you fence out functions (e.g. os.system ("rm -rf /"), see also Eval really is dangerous).
实际上，几乎所有现有的异常都可以抛出，并且任何代码的评估都可能造成任何破坏，除非您将函数隔离开来（例如os.system ("rm -rf /")，另请参阅Eval 真的很危险）。
回答by Vestel
Eval usually raises SyntaxError, you can cover your code with
Eval 通常会引发 SyntaxError，你可以用
try:
a = eval('1+2)+3')
except SyntaxError:
pass
Remember, you can isolate evalfrom accessing any functions passing { '__builtin__': None }as second parameter.
请记住，您可以隔离eval访问{ '__builtin__': None }作为第二个参数传递的任何函数。
