在python中動態創建類和__repr__

Question

這是一個相當直接的問題，希望你們都能啓發我。在下面的例子中，我如何定義__repr__被動態設置爲self.name？

謝謝大家！

import re 

inputlist = 'Project="Sparcy" Desc=""\nProject="Libs" Desc=""\nProject="Darwin" Desc=""\nProject="Aaple" Desc="The big project"' 

regex = re.compile('([^ =]+) *= *("[^"]*"|[^ ]*)') 

results = [] 
for project in inputlist.split("\n"): 
    items = [ (k.strip(), v.strip()) for k, v in regex.findall(project)] 
    if len(items) < 2: 
     print("Houston we have a problem - Only %s k/v pair found for %s" % (len(items), project)) 
     continue 
    item_dict = dict(items[1:]) 
    item_dict['name'] = items[0][1] 
    klass = type(items[0][0], (object,), item_dict) 
    results.append(klass) 

print results 

我所尋找的是這個

僞代碼

for result in results 
type(result) → Project 
print result → Sparky 

Answer 1

我猜你想

print results 

返回

["Sparcy", "Libs", "Darwin", "Aaple"] 

1. 打印列表顯示其元素的repr。
2. repr(elt)由type(elt).__repr__決定。
3. 由於在這種情況下元素是類，因此您需要爲該類的類型設置 __repr__。

---

import re 

inputlist = '''\ 
Project="Sparcy" Desc="" 
Project="Libs" Desc="" 
Project="Darwin" Desc="" 
Project="Aaple" Desc="The big project" 
Site="Phoenix" Protocol="Cheese"''' 

regex = re.compile('([^ =]+) *= *("[^"]*"|[^ ]*)') 

results = [] 
for project in inputlist.split("\n"): 
    items = [ (k.strip(), v.strip()) for k, v in regex.findall(project)] 
    if len(items) < 2: 
     print("Houston we have a problem - Only %s k/v pair found for %s" % (len(items), project)) 
     continue 
    item_dict = dict(items[1:]) 
    item_dict['name'] = items[0][1] 
    projectname=items[0][0] 
    metametaklass=type('meta_'+projectname,(type,),{'__repr__':lambda cls: cls.__name__}) 
    metaklass=metametaklass(projectname,(type,),{'__repr__':lambda cls: cls.name}) 
    klass=metaklass(projectname+'_class', (object,), item_dict) 
    results.append(klass) 

print(results) 

產生

["Sparcy", "Libs", "Darwin", "Aaple", "Phoenix"] 

和

for result in results: 
    print(type(result)) 
    print(result)  
    print('-'*80) 

產量

Project 
"Sparcy" 
-------------------------------------------------------------------------------- 
Project 
"Libs" 
-------------------------------------------------------------------------------- 
Project 
"Darwin" 
-------------------------------------------------------------------------------- 
Project 
"Aaple" 
-------------------------------------------------------------------------------- 
Site 
"Phoenix" 
-------------------------------------------------------------------------------- 

PS。請注意，這是__repr__的變形，因爲對象的repr應該是對象的明確字符串表示形式。也就是說，它應該提供足夠的信息來重現對象。你可能應該定義一個不同的print函數，而不是與元類混淆。