Question

我有以下条件声明：

if (sc == 'Both') and (fc == 'True') or (bc == 'True'):
     do this
if (sc == 'Front') and (fc == 'True'):
     do this
if (sc == 'Back') and (bc == 'True'):
    do this

问题是第二个和第三个子句按预期工作，但是，如果sc等于fc和bc都为假，则该语句仍然执行，我不知道原因。

Answer 1

你写了

if ((sc == 'Both') and (fc == 'True')) or (bc == 'True'):
     do this
if (sc == 'Front') and (fc == 'True'):
     do this
if (sc == 'Back') and (bc == 'True'):
    do this

我认为你的意思是

#                                     or binds weaker than and so it needs brackets
if (sc == 'Both') and ((fc == 'True') or (bc == 'True')):
     do this
if (sc == 'Front') and (fc == 'True'):
     do this
if (sc == 'Back') and (bc == 'True'):
    do this

您可以and和or对数字的任何操作都较弱，所以这也是正确的：

if sc == 'Both' and (fc == 'True' or bc == 'True'):
     do this
if sc == 'Front' and fc == 'True':
     do this
if sc == 'Back' and bc == 'True':
    do this

Python语句总是被执行帮助

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