Question

我正在尝试实现python REPL。

while True:
    exec("print repr("+raw_input(">>")+ ")")

测试输出：

>>1+1
2
>>"foo "+"bar"
'foo bar'
>>a=3

Traceback (most recent call last):
  File "/Users/user/Projects/python/custom_interpreter.py", line 2, in <module>
    exec("print repr("+raw_input(">>")+ ")")
  File "<string>", line 1, in <module>
TypeError: repr() takes no keyword argument

显然a = 3被评估为关键字参数而不是赋值操作。所以我改变了代码如下

import traceback
import sys
while True:
    cmd = raw_input(">>>")
    try:
        exec "print repr("+ cmd + ")"
    except TypeError:
        try:
            exec cmd
        except Exception as e:
            sys.stdout.write(traceback.format_exc())
    except Exception as e:
        sys.stdout.write(traceback.format_exc())

测试输出：

>>>a=1
>>>a
1
>>>b=2
>>>b+a
3
>>>"foo "+"bar"
'foo bar'
>>>"foo "+1
Traceback (most recent call last):
  File "/Users/user/Projects/spoj/python/MIXTURES/stack.py", line 9, in <module>
    exec cmd
  File "<string>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects
>>>exit()

Process finished with exit code 0

上面的代码是否提供了与python REPL相同的功能？

这个自定义实现的python Read Eval Print循环是否等同于python REPL

0 个答案: