使用pickle保存,读取文件

#dump.py
import pickle
try:
        with open(‘data.pickle‘,‘wb‘) as data:
            pickle.dump([1,2,‘three‘],data)

except IOError as err:
        print(‘file error:‘ + str(err))
except pickle.PickleError as perr:
        print(‘pickling error:‘ + str(perr))

#load.py
import pickle
try:
        with open(‘data.pickle‘,‘rb‘) as data:
                a_list = pickle.load(data)
                print a_list
except IOError as err:
        print(‘file error:‘+str(err))
except pickle.PickleError as perr:
        print(‘pickling error:‘+str(perr))

$ python dump.py
$ python load.py
[1, 2, ‘three‘]

第五章 处理数据

读取从head first python网站下载的四个成绩数据并格式化数据:

#print_times.py
def print_times(file_name):
    time_list = []
    try:
            with open(file_name+‘.txt‘) as data:
                    time_list = data.read().replace(‘-‘,‘:‘).replace(‘.‘,‘:‘)
                    time_list =  time_list.strip().split(‘,‘)
    except IOError as err:
            print(‘file error:‘+str(err))
    return time_list

>>> import print_times
>>> james = print_times.print_times(‘james‘)
>>> james
[‘2-34‘, ‘3:21‘, ‘2.34‘, ‘2.45‘, ‘3.01‘, ‘2:01‘, ‘2:01‘, ‘3:10‘, ‘2-22‘]
>>> julie = print_times.print_times(‘julie‘)
>>> julie
[‘2.59‘, ‘2.11‘, ‘2:11‘, ‘2:23‘, ‘3-10‘, ‘2-23‘, ‘3:10‘, ‘3.21‘, ‘3-21‘]
>>> mikey = print_times.print_times(‘mikey‘)
>>> mikey
[‘2:22‘, ‘3.01‘, ‘3:01‘, ‘3.02‘, ‘3:02‘, ‘3.02‘, ‘3:22‘, ‘2.49‘, ‘2:38‘]
>>> sarah = print_times.print_times(‘sarah‘)
>>> sarah
[‘2:58‘, ‘2.58‘, ‘2:39‘, ‘2-25‘, ‘2-55‘, ‘2:54‘, ‘2.18‘, ‘2:55‘, ‘2:55‘]
>>>

• mac终端中可用ctrl+a,ctrl+e快捷键跳至行首或行尾

推导列表

将一个列表以某种规则转换为另一个列表

>>>james = print_times.print_times(‘james‘)
>>> james
[‘2:34‘, ‘3:21‘, ‘2:34‘, ‘2:45‘, ‘3:01‘, ‘2:01‘, ‘2:01‘, ‘3:10‘, ‘2:22‘]
>>> jamesLee = [t.replace(‘:‘,‘-‘) for t in james]
>>> jamesLee
[‘2-34‘, ‘3-21‘, ‘2-34‘, ‘2-45‘, ‘3-01‘, ‘2-01‘, ‘2-01‘, ‘3-10‘, ‘2-22‘]

排序

• sort()提供原地排序,不保存原来的顺序
• sorted()复制排序,返回一个排序后的副本
• 默认排序方式为升序,降序可传参数reverse=True

使用集合去除列表重复项

>>> james
[‘2:01‘, ‘2:01‘, ‘2:22‘, ‘2:34‘, ‘2:34‘, ‘2:45‘, ‘3:01‘, ‘3:10‘, ‘3:21‘]
>>> unique = set(james)
>>> unique
set([‘2:45‘, ‘3:21‘, ‘2:01‘, ‘2:22‘, ‘2:34‘, ‘3:10‘, ‘3:01‘])
>>> james = list(unique)
>>> james
[‘2:45‘, ‘3:21‘, ‘2:01‘, ‘2:22‘, ‘2:34‘, ‘3:10‘, ‘3:01‘]