如何从文件创建嵌套字典列表

Question

I have an input text file containing a list of key/value pairs that I would like to read into python as a list of dictionaries but can not seem to get it to work as expected. Note that the file is not in valid json format so I can not use the json built-in and this question is not a duplicate of this . I suspect that I am missing something obvious here so any guidance is much appreciated.

# /tmp/tmp.txt
[{'k1': {'k2': {'k3': ['a', 'b', 'c']}}}, {'k4': {'k5': {'k6': ['v', 'x', 'y', 'z']}}}]

Since this file contains a list with 2 elements, I would expect the len to be 2 and the type to be list but that is not what I'm seeing.

with open('/tmp/tmp.txt', encoding='utf-8') as data_file:
    data = data_file.read()

print(len(data)) # <-- the goal is for this to show 2
print(type(data)) # <-- the goal is for this to return `list`

Output:

88
<class 'str'>

Answer 1

Your data is a string. You can convert it to a list with literal_eval :

import ast
data_list = ast.literal_eval(data)
len(data_list)
#2

Answer 2

EDIT: I didn't saw earlier that DYZ answered before me but I would like to explain my answer a bit more.

There is a module called 'ast' that have the function 'literal_eval', as the name suggest, it evaluates the information of the txt as python code and also validates the input.

import os, ast

with open('/tmp/tmp.txt', encoding='utf-8') as data_file:
    data = ast.literal_eval(data_file.read())

print(len(data))
print(type(data))

Output:

2
<class 'list'>

Answer 3

If you're trying to store and retrieve Python objects, serialization is probably a better way to go. See, for example, the pickle module .

But, in the present context, you could use the built-in Python eval function to accomplish your goal.