Python 2.7.5 (default, May 15 2013, 22:43:36) [MSC v.1500 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
#4.1字典的使用
>>> names=['Alice','Beth','Cecil','Dee-Dee','Earl']
>>> numbers=['2341','9102','3158','042','5551']
>>> names=['Alice','Beth','Cecil','Dee-Dee','Earl']
>>> numbers=['2341','9102','3158','042','5551']
>>> numbers[names.index('Cecil')]
'3158'
>>> 0142
98
>>> 0912
SyntaxError: invalid token
>>> 0812
SyntaxError: invalid token
#4.2创建和使用字典
>>> phonebook={'Alice':'2341','Beth':'9102','Cecil':'3258'}
>>> phonebook['Cecil']
'3258'
#4.2.1 dict函数
>>> items=[('name','Gumby'),('age',42)]
>>> d = dict(items)
>>> d
{'age': 42, 'name': 'Gumby'}
>>> d['name']
'Gumby'
>>> d = dict(name='Gumby', age=42)
>>> d
{'age': 42, 'name': 'Gumby'}
#4.2.2 基本字典操作
#len(d)返回d中项(键值对)的数量
#d[k]返回关联到键k上的值
#d[k]=v将值v关联到键k上
#del d[k]删除键为k的项
#k in d检查d中是否包括键为k的项
#键的类型:字典的键能够是整型,浮点型(实型),字符串或元组. 字典的键能够是不论什么不可变类型.
#在字典中检查键的成员资格比在列表中检查值的成员资格更有效,数据结构的规模越大,两者的效率差距越明显
>>> x=[]
>>> x[42]='Foobar'
Traceback (most recent call last):
File "<pyshell#24>", line 1, in <module>
x[42]='Foobar'
IndexError: list assignment index out of range
>>> x={}
>>> x[42]='Foobar'
>>> x
{42: 'Foobar'}
#代码清单4-1 字典演示样例
#4.2.3 字典的格式化字符串
>>> phonebook
{'Beth': '9102', 'Alice': '2341', 'Cecil': '3258'}
>>> "Cecil's phone number is %(Cecil)s. " % phonebook
"Cecil's phone number is 3258. "
>>> template = '''<html>
<head><title>%(title)s</title></head>
<body>
<h1>%(title)s</h1>
<p>%(text)s</p>
</body>'''
>>> data = {'title':'My Home Page', 'text':'Welcome to my home page!'}
>>> print template % data
<html>
<head><title>My Home Page</title></head>
<body>
<h1>My Home Page</h1>
<p>Welcome to my home page!</p>
</body>
#4.2.4 字典方法
#1.clear方法
>>> d={}
>>> d['name']='Gumby'
>>> d['age']=42
>>> d
{'age': 42, 'name': 'Gumby'}
>>> returned_value = d.clear()
>>> d
{}
>>> print returned_value
None
>>> x={}
>>> y=x
>>> x['key']='value'
>>> y
{'key': 'value'}
>>> x={}
>>> y
{'key': 'value'}
>>>
>>> x={}
>>> y=x
>>> x['key']='value'
>>> y
{'key': 'value'}
>>> x.clear()
>>> y
{}
#2.copy方法,这种方法实现的是浅复制(shallow copy)
>>> x={'username':'admin', 'machines':['foo','bar','baz']}
>>> y=x.copy()
>>> y['username']='mlh'
>>> y['machines'].remove('bar')
>>> y
{'username': 'mlh', 'machines': ['foo', 'baz']}
>>> x
{'username': 'admin', 'machines': ['foo', 'baz']}
#使用深复制(deep copy), 复制一个副本
>>> from copy import deepcopy
>>> d={}
>>> d['names']=''Alfred','Bertrand']
SyntaxError: invalid syntax
>>> d['anmes']=['Afred','Bertrand']
>>> c=d.copy()
>>> c
{'anmes': ['Afred', 'Bertrand']}
>>> d['names']=['Alfred','Bertrand']
>>> d
{'names': ['Alfred', 'Bertrand'], 'anmes': ['Afred', 'Bertrand']}
>>> d.clear()
>>> d['names']=['Alfred','Bertrand']
>>> c=d.copy()
>>> c
{'names': ['Alfred', 'Bertrand']}
>>> dc=deepcopy(d)
>>> d['names'].append('Clive')
>>> c
{'names': ['Alfred', 'Bertrand', 'Clive']}
>>> dc
{'names': ['Alfred', 'Bertrand']}
#3.fromkeys方法
>>> {}.fromkeys(['name','age'])
{'age': None, 'name': None}
>>> dict.fromkeys(['name','age'])
{'age': None, 'name': None}
>>> dict.fromkeys(['name','age'], '(unknown)')
{'age': '(unknown)', 'name': '(unknown)'}
>>>
#4.get方法
>>> d={}
>>> print d['name']
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
print d['name']
KeyError: 'name'
>>> print d.get['name']
Traceback (most recent call last):
File "<pyshell#2>", line 1, in <module>
print d.get['name']
TypeError: 'builtin_function_or_method' object has no attribute '__getitem__'
>>> print d.get('name')
None
>>> d.get('name','N/A')
'N/A'
>>> d['name']='Eric'
>>> d.get('name')
'Eric'
#代码清单4-2 字典方法演示样例
#5.has_key方法
>>> d={}
>>> d.has_key('name')
False
>>> d['name']='Eric'
>>> d.has_key('name')
True
#6.items和iteritems
>>> d={'title':'Python Web Site', 'url':'http://www.python.org', 'spam':0}
>>> d.items()
[('url', 'http://www.python.org'), ('spam', 0), ('title', 'Python Web Site')]
>>> it = d.iteritems()
>>> it
<dictionary-itemiterator object at 0x0134AF30>
>>> list(it) #Convert the iterator to a list
[('url', 'http://www.python.org'), ('spam', 0), ('title', 'Python Web Site')]
#7.keys方法和iterkeys方法
#keys方法将字典中的键以列表形式返回,而iterkeys则返回键的迭代器
#8.pop方法
>>> d = {'x':1, 'y':2}
>>> d.pop('x')
1
>>> d
{'y': 2}
>>>
#9.popitem方法
>>> d={'url':'http://www.python.org', 'spam':0, 'title':'Python Web Site'}
>>> d
{'url': 'http://www.python.org', 'title': 'Python Web Site', 'spam': 0}
>>> d.popitem()
('url', 'http://www.python.org')
>>> d
{'title': 'Python Web Site', 'spam': 0}
>>> d={}
>>> d.setdefault('name', 'N/A')
'N/A'
>>> d
{'name': 'N/A'}
>>> d['name']='Gumby'
>>> d.setdefault('name','N/A')
'Gumby'
>>> d
{'name': 'Gumby'}
>>> d={}
>>> print d.setdefault('name')
None
>>> d
{'name': None}
#11.update方法
>>> d={
'title':'Python Web Site',
'url':'http://www.python.org',
'changed':'Mar 14 22:09:15 MET 2008'
}
>>> x={'title':'Python Language Website'}
>>> d.update(x)
>>> d
{'url': 'http://www.python.org', 'changed': 'Mar 14 22:09:15 MET 2008', 'title': 'Python Language Website'}
#12. values方法和itervalues方法
>>> d={}
>>>
>>> d[1]=1
>>> d[2]=2
>>> d[3]=3
>>> d[4]=1
>>> d.values()
[1, 2, 3, 1]
>>>
#4.3 小结
#映射:映射能够使用不论什么不可变对象标识元素. 最经常使用的类型是字符串和元组. Python唯一内建的映射类型是字典.
#利用字典格式化字符串
#字典的方法
#4.3.1本章的新函数
#dict(seq) 用(键,值)对(或者映射和keyword參数)建立字典
字典演示样例
#coding=utf-8
#e4-1.py 字典演示样例
#简单数据库
#使用人名作为键的字典,每一个人用还有一个字典来表示,其键'phone'和'addr'分别表示他们的电话号码和地址.
people = {
'Alice': {
'phone':'2341',
'addr':'Foo drive 23'
},
'Beth': {
'phone':'9102',
'addr':'Bar street 42'
},
'Cecil':{
'phone':'3158',
'addr':'Baz avenue 90'
}
}
#针对电话号码和地址使用的描写叙述性标签, 会在打印输出的时候用到
labels = {
'phone':'phone number',
'addr':'address'
}
name=raw_input('Name: ')
#查找电话号码还是地址?
使用正确的键:
request = raw_input('Phone number (p) or address (a)?
')
#使用正确的键:
if request == 'p': key = 'phone'
if request == 'a': key = 'addr'
#假设名字是字典中的有效键才信息打印:
if name in people: print "%s's %s is %s. " % (name, labels[key], people[name][key])
#python e4-1.py
#Name: Beth
#Phone number (p) or address (a)? p
#Beth's phone number is 9102.
字典方法演示样例
#coding=utf-8
#e4-2
#使用get()的简单数据库
#这里加入代码清单4-1中插入数据库的代码
people = {
'Alice': {
'phone':'2341',
'addr':'Foo drive 23'
},
'Beth': {
'phone':'9102',
'addr':'Bar street 42'
},
'Cecil':{
'phone':'3158',
'addr':'Baz avenue 90'
}
}
labels = {
'phone':'phone number',
'addr':'address'
}
name = raw_input('Name: ')
#查找电话号码还是地址?
request = raw_input('Phone number (p) or address(a)? ')
#使用正确的键
key = request #假设请求既不是'p'也不是'a'
if request == 'p' : key = 'phone'
if request == 'a' : key = 'addr'
#使用get()提供默认值:
person = people.get(name, {})
label = labels.get(key ,key)
result = person.get(key, 'not available')
print "%s's %s is %s. " % (name, label, result)
#python e4-2.py
#Name: Beth
#Phone number (p) or address(a)? a
#Beth's address is Bar street 42.
#python e4-2.py
#Name: Cecil
#Phone number (p) or address(a)? p
#Cecil's phone number is 3158.
#python e4-2.py
#Name: Cecil
#Phone number (p) or address(a)?
x
#Cecil's x is not available.
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时间： 2024-08-08 05:34:47