在函数内部调用时，dict理解中出现Python名称错误

Question

我有以下python2代码，它给出了一个NameError：

def myfunc():


   myvar=50
    print myvar
    print eval('myvar')
    a = 'myvar'
    print { a:eval(a) }
    print { a:a for a in ['myvar'] }
    print { a:eval(a) for a in ['myvar'] }

myfunc()

当我现在用python2执行这个python代码时，我得到以下输出：

50
50
{'myvar': 50}
{'myvar': 'myvar'}
Traceback (most recent call last):
  File "tester.py", line 13, in <module>
    myfunc()
  File "tester.py", line 11, in myfunc
    print { a:eval(a) for a in ['myvar'] }
  File "tester.py", line 11, in <dictcomp>
    print { a:eval(a) for a in ['myvar'] }
  File "<string>", line 1, in <module>
NameError: name 'myvar' is not defined

备注：这是在Mac上运行的。。。 当我在函数外运行代码段时，它会按预期工作。。。你知道吗

Answer 1

你可以通过做。。。你知道吗

globs, locs = globals(), locals()
print { a:eval(a, globs, locs) for a in ['myvar'] }

这里可以找到一个解释：eval fails in list comprehension