字典的更新，遍历

dict={"a":"apple","b":"banana","c":"grape","d":"orange"}
print'输出key的列表'
print dict.keys()
print'输出value的列表'
print dict.values()
print'每个元素是一个key和value组成的元组，以列表的方式输出'
print dict.items()
print
dict={"a":"apple","b":"banana","c":"grape","d":"orange"}
it = dict.iteritems()
print it
print


print'字典中元素的获取方法'
dict={"a":"apple","b":"banana","c":"grape","d":"orange"}
print dict
print dict.get("d","apple")
print dict.get("c","apple")
print'get()的等价语句'
D={"key1":"value1","key2":"value2"}
if "key1" in D:
    print D["key1"]
else:
    print"None"


print
print'字典的更新'
dict={"a":"apple","b":"banana"}
print dict
dict2={"c":"grape","d":"orange"}
dict.update(dict2)
print dict


print
print'update()的等价语句'
D ={"key1":"value1","key2":"value2"}
E ={"key3":"value1","key4":"value2"}
for k in E:
    D[k]=E[k]
print D


print
print'字典E中含有字典D中的key'
D ={"key1":"value1","key2":"value2"}
E ={"key3":"value1","key4":"value2"}
for k in E:
    D[k]=E[k]
print D


print
print'设置默认值'
dict={}
dict.setdefault("a")
print dict
dict["a"]="apple"
dict.setdefault("a","default")

print dict

======================= RESTART: C:/Python27/dict1.py =======================
输出key的列表
['a', 'c', 'b', 'd']
输出value的列表
['apple', 'grape', 'banana', 'orange']
每个元素是一个key和value组成的元组，以列表的方式输出
[('a', 'apple'), ('c', 'grape'), ('b', 'banana'), ('d', 'orange')]


<dictionary-itemiterator object at 0x02520780>


字典中元素的获取方法
{'a': 'apple', 'c': 'grape', 'b': 'banana', 'd': 'orange'}
orange
grape
get()的等价语句
value1


字典的更新
{'a': 'apple', 'b': 'banana'}
{'a': 'apple', 'c': 'grape', 'b': 'banana', 'd': 'orange'}


update()的等价语句
{'key3': 'value1', 'key2': 'value2', 'key1': 'value1', 'key4': 'value2'}


字典E中含有字典D中的key
{'key3': 'value1', 'key2': 'value2', 'key1': 'value1', 'key4': 'value2'}


设置默认值
{'a': None}
{'a': 'apple'}
>>>