如何检查变量是否为空？

Question

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，它应该打印Shanaya如果主机名存在比打印byee。和主机名值从另外一个程序来有时说到有时不

Answer 1

如何：

class dheepak(): 
    age = 23 
    name = "dheepak sasi" 

ankit = getattr(dheepak, "hostname", '') 
if not ankit: 
    print "Shanaya" 
else: 
    print "byee" 
mani = dheepak.age 

print ankit 

Answer 2

您提供一个空间为ankit的值，如果没有这样的属性，但检查None。是一致的：

ankit = getattr(dheepak, "hostname", None) 
if ankit is None: 
    ... 

或

ankit = getattr(dheepak, "hostname", ' ') 
if ankit == ' ': 
    ... 

更重要的是，不要试图在所有定义的标记值;只要在该属性不存在时捕获由getattr引发的异常。

try: 
    ankit = getattr(dheepak, "hostname") 
except AttributeError: 
    print "Shanaya" 
else: 
    print "byee"