Python: Accessing dictionary from txt file and adding new data to it and then storing this updted dict back in txt file [closed]

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I have a dictionary in a text file in exact format given bellow,

 {'one': 'a', 'two': 'b', 'three': 'c'}

I want to take that dictionary in a variable say dict1. My program generates new key value pairs, if the new generated key is is not present in dict1 then I want to add this new key in dict1. finally I want to update txt file with this updated dictionary.

I know how to add key value pairs to a dict but I am not able to read that dictionary from txt file into a dictionary type of variable.

can anybody help plz ?

something like stackoverflow.com/questions/3277503/… is how to read a text file — depperm
– depperm, Commented Dec 17, 2015 at 17:29
"I am not able to read that dictionary from txt file into a dictionary type of variable" <- why, what's the problem? — timgeb
– timgeb, Commented Dec 17, 2015 at 17:35
How was this file written in the first place? You need to know the rules used for serialization before you can figure out how to parse it again. — tdelaney
– tdelaney, Commented Dec 17, 2015 at 17:43

FooBar · Accepted Answer · 2016-01-09 11:42:56Z

2

This piece of code works for me:

import ast

dict_file = open("dict.txt", "r")
dict_string = dict_file.readline().strip()
dict_file.close()

d = ast.literal_eval(dict_string)
print d["one"]

#change your dictionary e.g:
d["foo"] = "bar"

f = open("dict.txt", "w")
f.write(str(d))
f.close()

It simply reads the string from the file and creates a dictionary using the "ast.literal_eval". You can then commit changes to the dictionary, convert it to a string and write it to the txt file.

You could alternatively use Pickle

edited Jan 9, 2016 at 11:42

answered Dec 17, 2015 at 17:40

FooBar

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2 Comments

Ritzor Over a year ago

after I have updated the dict how to store updated dict to that dict.txt file?

FooBar Over a year ago

@Ritzor I have updated the answer

JCVanHamme · Accepted Answer · 2015-12-17 17:40:44Z

1

If your text file is named foo.txt, then

import json

with open('foo.txt', 'r') as f:
    d = json.load(f)

new_key = 'foo'
if new_key not in d:
    d[new_key] = 'bar'
    with open('foo.txt', 'w') as f:
        json.dump(d, f)

answered Dec 17, 2015 at 17:40

JCVanHamme

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2 Comments

wkl Over a year ago

If his file is formatted as he's shown, your code's going to throw an exception because of the single quotes. He'll need " everywhere to make it JSON-compatible.

tdelaney Over a year ago

OP didn't show us JSON so this can't really be considered an answer.

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