How to check whether a variable is empty?
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1 2 3 4 5 6 7 8 9 10 11 12 | class dheepak(): age = 23 name ="dheepak sasi" ankit = getattr(dheepak,"hostname", ' ') if ankit == None: print"Shanaya" else: print"byee" mani = dheepak.age print ankit |
如果主机名不存在,则应打印shanaya,如果主机名存在,则打印byee。主机名值来自另一个程序,有时不来自
如果没有这样的属性,您将提供一个空间作为
1 2 3 | ankit = getattr(dheepak,"hostname", None) if ankit is None: ... |
或
1 2 3 | ankit = getattr(dheepak,"hostname", ' ') if ankit == ' ': ... |
更好的是,不要试图定义一个sentinel值;只需捕获
1 2 3 4 5 6 | try: ankit = getattr(dheepak,"hostname") except AttributeError: print"Shanaya" else: print"byee" |
这个怎么样?
1 2 3 4 5 6 7 8 9 10 11 12 | class dheepak(): age = 23 name ="dheepak sasi" ankit = getattr(dheepak,"hostname", '') if not ankit: print"Shanaya" else: print"byee" mani = dheepak.age print ankit |