Python core programming version 2 Chapter 7 Exercise 1

7-3.
Dictionary and list methods.
(A) Create a dictionary and display the keys in the dictionary alphabetically.
(B) the keys and values in the dictionary are displayed in alphabetical order.
(C) Same as (B), but this time the keys and values in the dictionary are displayed based on the values in alphabetical order (NOTE: For the dictionary and hash table, this generally makes no practical sense, because most access and sorting (if needed) are dictionary-based keys. Here we only use it as an exercise ).
[Answer]
(A) The Code is as follows:
>>> My_dict = {'A': 4, 'B': 3, 'C': 2, 'D': 1}
>>> My_dict
{'A': 4, 'C': 2, 'B': 3, 'D': 1}
>>> My_dict.values ()
[4, 2, 3, 1]
>>> My_dict.keys ()
['A', 'C', 'B', 'D']
>>> Sorted (my_dict.keys ())
['A', 'B', 'C', 'D']
>>>
(B) The Code is as follows:
>>> For I in sorted (my_dict.keys ()):
... Print 'key = % s, value = % d' % (I, my_dict [I])
...
Key = a, value = 4
Key = B, value = 3
Key = c, value = 2
Key = d, value = 1
>>>
(C) The Code is as follows:
>>> Dic = {'A _ key': 5, 'B _ key': 4, 'c _ key': 3, 'd _ key': 2, 'E _ key': 1}
>>> K = sorted (dic. iteritems (), key = lambda asd: asd [1], reverse = False)
>>> For I in range (len (k): print k [I] [0], k [I] [1]
...
E_key 1
D_key 2
C_key 3
B _key 4
A_key 5
>>>

[Reference]
About function lambda

>>> Dic = {'A _ key': 5, 'B _ key': 4, 'c _ key': 3, 'd _ key': 2, 'E _ key': 1}
>>> Dic
{'E _ key': 1, 'B _ key': 4, 'A _ key': 5, 'd _ key': 2, 'c _ key ': 3}

>>> Print dic. iteritems ()
<Dictionary-itemiterator object at 0x00A75A50>
>>> Print type (dic. iteritems ())
<Type 'dictionary-itemiterator'>

>>> For I in dic. iteritems ():
... Print I
...
('E _ key', 1)
('B _ key', 4)
('A _ key', 5)
('D _ key', 2)
('C _ key', 3)

>>> For I in dic. iteritems ():
... Print I [0], I [1], I
...
E_key 1 ('e _ key', 1)
B _key 4 ('B _ key', 4)
A_key 5 ('A _ key', 5)
D_key 2 ('d _ key ', 2)
C_key 3 ('C _ key', 3)

>>> Print sorted (dic. iteritems ())
[('A _ key', 5), ('B _ key', 4), ('C _ key', 3), ('d _ key ', 2), ('e _ key', 1)]

>>> F = lambda x: x + 1
>>> F (2)
3
# What is a lambda function? X is the parameter, and x + 1 is the return value of the function.

>>> Print sorted (dic. iteritems (), key = lambda asd: asd [0])
[('A _ key', 5), ('B _ key', 4), ('C _ key', 3), ('d _ key ', 2), ('e _ key', 1)]

>>> Print sorted (dic. iteritems (), key = lambda asd: asd [1])
[('E _ key', 1), ('d _ key', 2), ('C _ key', 3), ('B _ key ', 4), ('A _ key', 5)]

>>> Print sorted (dic. iteritems (), key = lambda asd: asd [1], reverse = True)
[('A _ key', 5), ('B _ key', 4), ('C _ key', 3), ('d _ key ', 2), ('e _ key', 1)]

>>> Print sorted (dic. iteritems (), key = lambda asd: asd [1], reverse = False)
[('E _ key', 1), ('d _ key', 2), ('C _ key', 3), ('B _ key ', 4), ('A _ key', 5)]

Python dictionary sorting
Http://hi.baidu.com/when_love/blog/item/b66b510143821709728da563.html

Python list sorting sort
Http://wupinyin.appspot.com/article_detail? Id = agh3dXBpbnlpbnIOCxIHQXJ0aWNsZRjyLgw

7-4.
Create a dictionary. Two lists with the same length are given. For example, the list is [1, 2, 3,...]. and ['abc', 'def', 'ghi',...], use all the data in these two lists to form a dictionary. Like this: {1: 'abc', 2: 'def ', 3: 'ghi ',...}.
[Answer]
The Code is as follows:
>>> List_a = [1, 2, 3, 4]
>>> List_ B = ['A _ value', 'B _ value', 'c _ value', 'd _ value']

>>> Zip (list_a, list_ B)
[(1, 'A _ value'), (2, 'B _ value'), (3, 'c _ value'), (4, 'd _ value')]

>>> C = {}

>>> K = zip (list_a, list_ B)
>>> K
[(1, 'A _ value'), (2, 'B _ value'), (3, 'c _ value'), (4, 'd _ value')]

>>> For I in range (len (k )):
... C. update ({k [I] [0]: k [I] [1]})
...

>>> C
{1: 'A _ value', 2: 'B _ value', 3: 'C _ value', 4: 'd _ value '}