CODEWITHSUNDEEP
pythonpython-3.xtree
Blake
Blake

Reputation: 35

How to read lines of a file to be lists instead of strings in python

I have a file where each line is a list representation of a tree. For example, one of these lines in the file is:

[1, [[2,[]], [3, [ [5,[]], [6, [ [10,[]] ] ] ]], [4, [ [7,[]], [8,[]], [9,[]] ]] ]]

If I copy and paste this into my program, it understands that it is a list and I can easily manipulate it to find the root and the children, and then take those children and find their children, etc. When I read a file line by line, it takes those lines and turns them into strings. If I try to convert these strings into lists then it takes each individual character in the string to be a different item in the list and thats not what I want.

I just want to know how I can read a file line by line but instead of it spitting out strings, it gives me each line in its literal list form. The file I'm reading is a .txt file and it must stay this way I cant save it as a .py file or anything like that.

Upvotes: 2

Views: 163

Answers (2)

Stefan Gruenwald
Stefan Gruenwald

Reputation: 2640

You can load a datafile into a list like this and the types will be handled correctly:

def load_lines():
    res=[]
    with open("datafile.txt","r+") as f:
        for line in f.readlines():
            a_line = [ast.literal_eval(text) for text in line.split(',')]
            res.append(a_line)
    return res

Upvotes: 0

rassar
rassar

Reputation: 5670

Try the ast module:

>>> s = "[1, [[2,[]], [3, [ [5,[]], [6, [ [10,[]] ] ] ]], [4, [ [7,[]], [8,[]], [9,[]] ]] ]]"
>>> l = ast.literal_eval(s)
>>> l[0]
1

Upvotes: 2

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