在不更新元组值的情况下有条件地添加到字典

Question

下面的函数附加了一对作为参数的不可变元组。在追加处理中，有必要用开始和结束单引号括起所有值。因为元组值是不可变的，我不能简单地这样做：

if item[1][0] != "'" and item[1][-1] != "'": 
    item[1] = "'{0}'".format(item[1]) 

self.keyvalues[item[0]] = item[1] 

因此，操作如下：

if item[1][0] != "'" and item[1][-1] != "'": 
    self.keyvalues[item[0]] = "'{0}'".format(item[1]) 
else: 
    self.keyvalues[item[0]] = item[1] 

的完整代码如下所示。

是否有一种更优雅的方式来将密钥和值添加到字典中。

class section(object): 
    """class to hold a section. name is name of section. keyvalues is a key 
    value dictionary of keys and values""" 
    def __init__(self, name): 
     self.name = name 
     self.keyvalues = {} 
     print "Constructed section:", name 

    def append(self, item): 
     """add a key value pair to section""" 
     if len(item) != 2: 
      return False 
     else: 
      print "adding:", item, "to", self.name, "object" 

      # cannot do this because tuple is immutable 
      #item[1] = "'{0}'".format(item[1]) 

      # Would there be a more elegant way of doing this - given that 
      # parameter must be a immutable tuple? 
      if item[1][0] != "'" and item[1][-1] != "'": 
       self.keyvalues[item[0]] = "'{0}'".format(item[1]) 
      else: 
       self.keyvalues[item[0]] = item[1] 
      return True 

    def __repr__(self): 
     s = "contains\n" 
     for k, v in self.keyvalues.iteritems(): 
      s += "\t{0}={1}\n".format(k, v) 
     return s 

    __str__ = __repr__  


mysection = section("section1") 
dnpair = ("key1", "value1") 
mysection.append(dnpair) 

print mysection 

Answer 1

由于元组不再使用，只是将其分割为单独的变量。

key, value = item 

if value[0] != "'" and value[-1] != "'": 
    value = "'{0}'".format(value) 

self.keyvalues[key] = value 

Answer 2

优雅是主观的，但这是我能想出的最优雅的解决方案。它允许通过将其传递给函数来进行值操作。另外，丑陋

if item[1][0] != "'" and item[1][-1] != "'": 

成为

if not value[0] == value[-1] == "'": 

下面是完整的代码修改append和新创建的quote_wrap方法。

def append(self, item): 
    """add a key value pair to section""" 
    if len(item) != 2: 
     return False 
    else: 
     print("adding:", item, "to", self.name, "object") 
     self.keyvalues[item[0]] = self.quote_wrap(item[1]) 
     return True 

def quote_wrap(self, value): 
    if not value[0] == value[-1] == "'": 
     value = "'{}'".format(value) 
    return value