python第五课：字典的功能

一.字典

1.字典的定义

user_info={

       "name":"alex"

       "age":"73"

       "gender":"m"

}

2功能

索引

• print（user_info[name]）
• print(user_info["age"])
• 无切片：因为索引值不连续
• 循环：默认输出key
• for i in use_info:
•   print(i)
• 获取所有的键：print(user_info.keys())
• 获取所有的值：print(user_info.values())
• 获取所有的键值对：print（user_info.items()）
• for k v in user_info.items():
•   print(k)
•   print(v)
• 删除指定键值对
• del user_info("age")

    def clear(self): # real signature unknown; restored from __doc__
       ------ 清楚所有内容-----
        """ D.clear() -> None.  Remove all items from D. """
        pass

    def copy(self): # real signature unknown; restored from __doc__
        """ D.copy() -> a shallow copy of D """
        pass

    @staticmethod # known case
    def fromkeys(S, v=None): # real signature unknown; restored from __doc__
        """
        dict.fromkeys(S[,v]) -> New dict with keys from S and values equal to v.
        v defaults to None.
        """
        pass

    def get(self, k, d=None): # real signature unknown; restored from __doc__
        根据key获取指定键值，如果不存返回默认值None
       """ D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None. """
        pass

    def has_key(self, k): # real signature unknown; restored from __doc__
       检查字典中是否有指定key值
     s=user_info.has_key()
     s="age" in user_info.key()
        """ D.has_key(k) -> True if D has a key k, else False """
        return False

    def items(self): # real signature unknown; restored from __doc__
        """ D.items() -> list of D's (key, value) pairs, as 2-tuples """
        return []

    def iteritems(self): # real signature unknown; restored from __doc__
        """ D.iteritems() -> an iterator over the (key, value) items of D """
        pass

    def iterkeys(self): # real signature unknown; restored from __doc__
        """ D.iterkeys() -> an iterator over the keys of D """
        pass

    def itervalues(self): # real signature unknown; restored from __doc__
        """ D.itervalues() -> an iterator over the values of D """
        pass

    def keys(self): # real signature unknown; restored from __doc__
        """ D.keys() -> list of D's keys """
        return []

    def pop(self, k, d=None): # real signature unknown; restored from __doc__
        ----获取并在字典中移除----
        """
        D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
        If key is not found, d is returned if given, otherwise KeyError is raised
        """
        pass

    def popitem(self): # real signature unknown; restored from __doc__
       ---获取并在字典中移除----
         """
        D.popitem() -> (k, v), remove and return some (key, value) pair as a
        2-tuple; but raise KeyError if D is empty.
        """
        pass

    def setdefault(self, k, d=None): # real signature unknown; restored from __doc__
      
       """ D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D """
        pass

    def update(self, E=None, **F): # known special case of dict.update
        ----批量更新-----
   test={ 
      "a1":123,
      "a2":456,
}
user_info.update(test)
print(user_info)

       """
        D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.
        If E present and has a .keys() method, does:     for k in E: D[k] = E[k]
        If E present and lacks .keys() method, does:     for (k, v) in E: D[k] = v
        In either case, this is followed by: for k in F: D[k] = F[k]
        """
        pass

    def values(self): # real signature unknown; restored from __doc__
        """ D.values() -> list of D's values """
        return []

    def viewitems(self): # real signature unknown; restored from __doc__
        """ D.viewitems() -> a set-like object providing a view on D's items """
        pass

    def viewkeys(self): # real signature unknown; restored from __doc__
        """ D.viewkeys() -> a set-like object providing a view on D's keys """
        pass

    def viewvalues(self): # real signature unknown; restored from __doc__
        """ D.viewvalues() -> an object providing a view on D's values """
        pass

3.enumerate ：为可迭代的对象添加序号

li=[''电脑","鼠标垫","U盘"]

for key item in enumerate(i)

   print(key,item)

4.range和xrange指定范围生成指定数字

python2.7 :range会直接打印所有数字，而xrange只会在for循环时打印

python3.5及以上版本，只有range，且range就相当于xrange。

print (xrange(1,10))

for i in range(1,10):

print(i)

输出从大到小的值

for i in range(1,10，-1):

print(i)

输出索引和值

li=['alex','scc']

lee=len(li)

for i in xrange(0,len(li))

print(i,li[i])