如何檢查變量是否爲空？

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 

如果主機名不存在，它應該打印Shanaya如果主機名存在比打印byee。和主機名值從另外一個程序來有時說到有時不

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

您提供一個空間爲ankit的值，如果沒有這樣的屬性，但檢查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，不要試圖在所有定義的標記值;只要在該屬性不存在時捕獲由getattr引發的異常。

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