python学习三(数据保存到文件）

以写模式打开文件:需要指定写模式，如下所示

data = open('data.out','w')

如果文件已经存在，则会清空它现有的所有内容。要追加一个文件，需要使用访问模式a，会追加到下一行。

例子：将上节中Man和Other Man说的话，分别保存到两个文件中

man = []
other = []

try:
    data = open('sketch.txt')

    for each_line in data:
        try:
            (role, line_spoken) = each_line.split(':')
            line_spoken = line_spoken.strip()
            if role == 'Man':
                man.append(line_spoken)
            elif role == 'Other Man':
                other.append(line_spoken)
            else:
                pass
        except ValueError:
            pass

    data.close()
except IOError:
    print('The datafile is missing!')
#使用print将列表中的数据输出到文件中
try:
    with open('man_data.txt', 'w') as man_file, open('other_data.txt', 'w') as other_file:
        print(man, file=man_file)
        print(other, file=other_file)
except IOError as err:
    print('File error: ' + str(err))

使用with open()方法保存文件，不需要再用close方法关闭文件

Python提供了一个标准库，名为pickle，它可以加载、保存几乎任何的Python数据对象，包括列表

使用python的dump保存，load恢复

import pickle

man = []
other = []

try:
    data = open('sketch.txt')

    for each_line in data:
        try:
            (role, line_spoken) = each_line.split(':')
            line_spoken = line_spoken.strip()
            if role == 'Man':
                man.append(line_spoken)
            elif role == 'Other Man':
                other.append(line_spoken)
            else:
                pass
        except ValueError:
            pass

    data.close()
except IOError:
    print('The datafile is missing!')

try:
    with open('man_data.txt', 'wb') as man_file, open('other_data.txt', 'wb') as other_file:
        pickle.dump(man, file=man_file)
        pickle.dump(other, file=other_file)
except IOError as err:
    print('File error: ' + str(err))
except pickle.PickleError as perr:
    print('Pickling error: ' + str(perr))
    

'wb'中的b表示以二进制模式打开文件

要读取二进制文件使用'rb'

import pickle
with open('man_data.txt','rb') as readText:
    a_list = pickle.load(readText)
print(a_list)