如何从python中的文件导入列表

Question

I have a file like f = [1,1,2,2,2,3,3,4,5] and i would like to import this file like a list So that it is treated as a list. eg say i have two files, one contain f = [1,1,1,1,1] and the second contain d = [2,2,2,2,2] and i would like to zip(i,j) for i in f and for j in d .

f = file('f.txt')
d = file('d.txt')

for i in f:
    for j in d:
        print zip(i,j)

The result is

[('[', '['), ('1', '2'), (',', ','), ('1', '2'), (',', ','), ('1', '2'), (',', ','), ('1', '2'), (',', ','), ('1', '2'), (']', ']'), ('\n', '\n')]

and i would like to be like

[(1,2),(1,2), (1,2),(1,2), (1,2)]

Answer 1

ast.literal_eval is a safe way to evaluate strings as Python literals (eg strings, numbers, tuples, lists, dicts, booleans, and None):

import ast
with open('f.txt') as f:
    with open('d.txt') as d:
        flist=ast.literal_eval(f.read())
        dlist=ast.literal_eval(d.read())
        print(zip(flist,dlist))

Answer 2

For one thing, you want the file to be parsed as Python text, but just reading its contents will only give you a string. Iterating over strings give you their characters one at a time.

So rather than just reading their contents, load them as modules: from f import f , from d import d

This requires that they live in a "package", ie a directory that is on your PYTHONPATH and has an __init__.py file in it, but it allows you to stay on the clean side of things.

Then just handle f and d as normal Python variables that hold lists.

Answer 3

If you have end to end control over this data, I would recommend serializing it with the pickle library rather than "serializing" the representations as text.

See http://docs.python.org/library/pickle.html#example for more info.

Answer 4

Another option would be the exec method, see my example below.

In [27]: x="f = [1,1,2,2,2,3,3,4,5]"
In [28]: exec(x)
In [29]: f
Out[29]: [1, 1, 2, 2, 2, 3, 3, 4, 5]

Specifically for your problem:

exec(file('f.txt').read())
exec(file('d.txt').read())    
print zip(f,d)

Produces the output:

[(1, 2), (1, 2), (1, 2), (1, 2), (1, 2)]