python：组合sort-key-functions itemgetter和str.lower [英] python: combine sort-key-functions itemgetter and str.lower

问题描述

 <$ 
我想按字典键对字典列表进行排序，我不想区分大写字母和小写字符。 c $ c> dict1 = {'name'：'peter'，'phone'：'12355'} 
 dict2 = {'name'：'Paul'，'phone'：'545435'} 
 dict3 = {'name'：'klaus'，'phone'：'55345'} 
 dict4 = {'name'：'Krishna'，'phone'：'12345'} 
 dict5 = {'名字'：'Ali'，'phone'：'53453'} 
 dict6 = {'name'：'Hans'，'phone'：'765756'} 
 list_of_dicts = [dict1，dict2，dict3 ，dict4，dict5，dict6] 
 
 key_field ='name'
 list_of_dicts.sort（key = itemgetter（key_field））
＃如何将key = itemgetter（key_field）和关键= str.lower？ 
 for list_field in list_of_dicts：
 print list_field [key_field] 
  

应该提供

  Ali，Hans，klaus，Krishna，Paul，peter 
  

而不是

 克劳斯，彼得，阿里，汉斯，克里希纳，保罗
  

解决方案

在一般情况下，您需要编写用于分类目的的密钥提取功能;只有在特殊情况下（尽管很重要），您可以重新使用现有的调用方法来为您提取密钥，或者只需结合现有的一些调用（使用 lambda的快速和肮脏方式，因为没有内置的函数组合方法）。

如果您经常需要执行这两种键提取操作（获取一个项目并调用该项目的方法），我建议：

  def combiner（itemkey，methodname，* a， ** k）：
 def keyextractor（容器）：
 item = container [itemkey] 
 method = getattr（item，methodname）
返回方法（* a，** k ）
 return keyextractor 
  

so listofdicts.sort（key = combiner （'name'，'lower'））将适用于您的情况。

请注意，过度泛化会导致成本，雅致和中等泛化（将项目键，方法名和方法参数（如果有的话）作为runtime-deter在这种情况下开采）通常具有优点 - 一个通用功能，不比十几个特定和专门的功能（使用提取器，方法调用，或两者，在他们的代码中硬连线）更复杂，将更容易维护（和，当然，重用起来要容易得多！ - ）。

I want to sort a list of dictionaries by dictionary key, where I don't want to distinguish between upper and lower case characters.

dict1 = {'name':'peter','phone':'12355'}
dict2 = {'name':'Paul','phone':'545435'}
dict3 = {'name':'klaus','phone':'55345'}
dict4 = {'name':'Krishna','phone':'12345'}
dict5 = {'name':'Ali','phone':'53453'}
dict6 = {'name':'Hans','phone':'765756'}
list_of_dicts = [dict1,dict2,dict3,dict4,dict5,dict6]

key_field = 'name'
list_of_dicts.sort(key=itemgetter(key_field))
# how to combine key=itemgetter(key_field) and key=str.lower? 
for list_field in list_of_dicts:
    print list_field[key_field]

should provide

Ali, Hans, klaus, Krishna, Paul, peter

and not

klaus, peter, Ali, Hans, Krishna, Paul

解决方案

In the general case, you'll want to write your key-extraction function for sorting purposes; only in special (though important) cases it happens that you can just reuse an existing callable to extract the keys for you, or just conjoin a couple of existing ones (in a "quick and dirty" way using lambda, since there's no built-in way to do function composition).

If you often need to perform these two kinds of operations for key extraction (get an item and call a method on that item), I suggest:

def combiner(itemkey, methodname, *a, **k):
  def keyextractor(container):
    item = container[itemkey]
    method = getattr(item, methodname)
    return method(*a, **k)
  return keyextractor

so listofdicts.sort(key=combiner('name', 'lower')) will work in your case.

Note that while excessive generalization has costs, tasteful and moderate generalization (leaving the item key, method name, and method arguments if any, as runtime-determined, in this case) generally has benefits -- one general function, not more complex than a dozen specific and specialized ones (with the extractor, method to call, or both, hardwired in their code), will be easier to maintain (and, of course, much easier to reuse!-).

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