从文件中写入和读取列表

Question

这是一个有点奇怪的请求,但我正在寻找一种方法将列表写入文件,然后在其他时间读回.

我没有办法重新制作列表,以便正确形成/格式化它们,如下例所示.

我的列表包含以下数据:

test
data
here
this
is one
group :)

test
data
here
this
is another
group :)

Answer 1

If you don't need it to be human-readable/editable, the easiest solution is to just use pickle.

To write:

with open(the_filename, 'wb') as f:
    pickle.dump(my_list, f)

To read:

with open(the_filename, 'rb') as f:
    my_list = pickle.load(f)

If you do need them to be human-readable, we need more information.

If my_list is guaranteed to be a list of strings with no embedded newlines, just write them one per line:

with open(the_filename, 'w') as f:
    for s in my_list:
        f.write(s + '\n')

with open(the_filename, 'r') as f:
    my_list = [line.rstrip('\n') for line in f]

If they're Unicode strings rather than byte strings, you'll want to encode them. (Or, worse, if they're byte strings, but not necessarily in the same encoding as your system default.)

如果他们可能有换行符或不可打印的字符等,您可以使用转义或引用.Python在stdlib中内置了各种不同类型的转义.

让我们一起unicode-escape用来解决上述两个问题:

with open(the_filename, 'w') as f:
    for s in my_list:
        f.write((s + u'\n').encode('unicode-escape'))

with open(the_filename, 'r') as f:
    my_list = [line.decode('unicode-escape').rstrip(u'\n') for line in f]

您还可以在2.x中使用3.x样式的解决方案,包括codecs模块或io模块:*

import io

with io.open(the_filename, 'w', encoding='unicode-escape') as f:
    f.writelines(line + u'\n' for line in my_list)

with open(the_filename, 'r') as f:
    my_list = [line.rstrip(u'\n') for line in f]

_{*TOOWTDI,这是一个显而易见的方法吗？这取决于...对于简短版本:如果您需要在2.6之前使用Python版本,请使用codecs; 如果没有,请使用io.}

Answer 2

只要您的文件具有一致的格式(即换行符),只需基本的文件IO和字符串操作就可以轻松实现:

with open('my_file.txt', 'rU') as in_file:
    data = in_file.read().split('\n')

这会将您的数据文件存储为项目列表,每行一个.然后把它放到一个文件中,你会做相反的事情:

with open('new_file.txt', 'w') as out_file:
    out_file.write('\n'.join(data)) # This will create a string with all of the items in data separated by new-line characters

希望这符合您的需求.

Answer 3

我们先定义一个列表：

lst=[1,2,3]

您可以直接将列表写入文件：

f=open("filename.txt","w")
f.write(str(lst))
f.close()

要从文本文件读取列表，首先要读取该文件并将其存储在变量中：

f=open("filename.txt","r")
lst=f.read()
f.close()

变量的类型lst当然是字符串。您可以使用函数将此字符串转换为数组eval。

f=open("filename.txt","r")
lst=f.read()
f.close()