python 字典与文件

python

字典

key-value

• dict = {'xiaoming':90, 'xiaohong':80,'xiaomao':60,'xiaoli':54}
• dict 生成字典
• zip 生成元组

常用操作

• key(不变的类型)，values(什么类型都行，也可以嵌套)
• get
• updrate
• del
• clear
• 嵌套
• 引用
• 浅拷贝 字典D.copy(), copy.copy(D) (列表：L[:])
• 深拷贝 copy.deepcopy(D)

字典的特点：
散列表，没有顺序，适合插入、查询操作
key不一定是字符串，但一定是不可变对象

排序

[(k,dict[k]) for k in sorted(dict.keys())]  //列表解析，排序结果存到list里
//调用函数
sorted(dict.iteritens().key=lambda d:d[1],
reverse = True

#--------用dict直接生成, 
name_age=(('xiaoli',33),('xiaowang',20),('xiaozhang',40))
a=dict(name_age)
a;      #{'xiaozhang': 40, 'xiaoli': 33, 'xiaowang': 20}
b=dict(xiaoli=33,xiaowang=20,xiaozhang=40)
b;      #{'xiaozhang': 40, 'xiaoli': 33, 'xiaowang': 20}
#--------如何将两个等长度的list合并成dict
text = 'c++ python shell ruby java javascript c'
code_num = [38599, 100931, 26153, 93142, 84275, 184220, 46843]
text_list=text.split(' ')
text_list;      #['c++', 'python', 'shell', 'ruby', 'java', 'javascript', 'c']
code_dict = dict(zip(text_list,code_num))
code_dict;      #{'c': 46843, 'shell': 26153, 'java': 84275, 'python': 100931, 'javascript': 184220, 'c++': 38599, 'ruby': 93142}
#--------key, keys, items, values
code_dict['python']     #100931
code_dict.keys()        #['c', 'shell', 'java', 'python', 'javascript', 'c++', 'ruby']
code_dict.values()      #[46843, 26153, 84275, 100931, 184220, 38599, 93142]
code_dict.items()
#[('c', 46843), ('shell', 26153), ('java', 84275), ('python', 100931), ('javascript', 184220), ('c++', 38599), ('ruby', 93142)]
#--------get
a=code_dict.get('fortran',None)     #空
a=code_dict.get('fortran','aaa')    #aaa
#------- ref and copy
a_ref = code_dict
a_copy = code_dict.copy()
#--------update, del, copy, clear
other_code = {'php':78014,'objective-c':34444}
code_dict.update(other_code)
#{'c': 46843, 'shell': 26153, 'java': 84275, 'python': 100931, 'javascript': 184220, 'c++': 38599, 'objective-c': 34444, 'php': 78014, 'ruby': 93142}
del code_dict['c++']
#{'c': 46843, 'shell': 26153, 'java': 84275, 'python': 100931, 'javascript': 184220, 'objective-c': 34444, 'php': 78014, 'ruby': 93142}
a_ref.clear()       #{}
#--------sort key and value
[(k,a_copy[k]) for k in sorted(a_copy.keys())]
#[('c', 46843), ('c++', 38599), ('java', 84275), ('javascript', 184220), ('objective-c', 34444), ('php', 78014), ('python', 100931), ('ruby', 93142), ('shell', 26153)]

文件

常用操作

• F=open（path,'r'）: 'path'包括路径与文件名。'r'表示读，类似的还有'w'表示写（无文件则新建，有则会先清空），'a'表示追加。返回对象为 file-like obiect
• F.read()
• F.readline() 读一行
• F.write()
• F.close()

• 中文支持

  import codecs
  f=codecs.open(filename, mode, encoding)

• 文件操作

  import os
  os.path.exists(filename)
  os.rename(old,new)

########################## file ################
import codecs
f=codecs.open('file_ch.txt','w','utf-8')
f.write(u'hello\n')
f.write(u'world\n')
f.write(u'hello python\n')
f.close()
#read file
f=codecs.open('file_ch.txt','r','utf-8')
print f.readline()      #hello
print f.readline()      #world
print f.readline()      #hello python
f.close()
########################## os ################
import os
print os.path.exists('file_ch.txt')     #true
os.rename('file_ch.txt', 'file_test.txt')
print os.path.exists('file_ch.txt')     #false

Shelve库

import shelve
D = shelve.open(file)
D[ 'name' ] = 'xiaoming'
D.close()

pickle/cPickle库

import cPickle
f=open(file,mode)
cPickle.dump(obj,f)
Obj = cPickle.load(f)

########################## shelve ################
import shelve
f = shelve.open('file_test.shelve')
f['baidu'] = 'www.baidu.com'
f['qq'] = 'www.qq.com'
f['163'] = 'www.163.com'
print f         
#{'qq': 'www.qq.com', 'baidu': 'www.baidu.com', '163': 'www.163.com'}
f.close()
g = shelve.open('file_test.shelve')
print g
#{'qq': 'www.qq.com', 'baidu': 'www.baidu.com', '163': 'www.163.com'}
########################## pickle ################
print "--------------------------------------"
import cPickle
f=open('file_test.pkl','w')
obj1 = 2015,"heibanke",[1,2,3,4],{"python":1990,"java":1992}
obj2 = ['heibanke','junmin11','chutianshu1981','sjtujoe','ygkkv',
'liuyanping_0904','zhkmxx930']
cPickle.dump(obj1,f)
cPickle.dump(obj2,f)
f.close()
#read file
f=open('file_test.pkl','r')
obj1_r = cPickle.load(f)
print obj1_r
#(2015, 'heibanke', [1, 2, 3, 4], {'python': 1990, 'java': 1992})
obj2_r = cPickle.load(f)
print obj2_r
f.close()
#['heibanke', 'junmin11', 'chutianshu1981', 'sjtujoe', 'ygkkv', 'liuyanping_0904', 'zhkmxx930']