How to read the dictionary from text file?

Question

I have a text file in the below format

d = {'EMS':1,'ESC': 2, 'HVAC': 3,'IC' : 4,'ICU' : 5,'IS' : 6,'ITM' : 7,'MBFM' : 8,'PKE' : 9,'RPAS' : 10,'RVC' : 11,'SAS' : 12,'SRS' : 13,'TCU' : 14,'TPMS' : 15,'VCU' : 16,'BMS' : 17,'MCU' :18,'OBC' :19}

How do I read the dictionary to find the value a particular value?

I have tried the below code

with open(r"filename","r") as f:
    data = ast.literal_eval(f.read())
    print(data)
    for age in data.values():
        if age == search_age:
            name = data[age]
            print (name)

@Tejesh Reddy remove the `d = ` from the file. Most likely this is the issue — Jab, Apr 24 '19 at 05:20
This is a valid python module. Rename it to `filename.py` and then `from filename import d`. That's it, now you've got your dictionary. — constt, Apr 24 '19 at 05:53

blhsing · Accepted Answer · 2019-04-24T05:50:40.420

Your text file is a valid Python code, so if it is from a trusted source, you can simply do:

with open("filename") as f:
    exec(f.read())

and the variable d would be loaded with the dict.

If the text file is not from a trusted source, however, you can use ast.parse to parse the code, then use ast.walk to traverse the abstract syntax tree and look for a Dict node. For security reasons, make sure the dict node does not contain any Call node before wrapping it as the body of an Expression node and compiling it for eval to turn it into a real dict stored in variable d:

import ast
with open("filename") as f:
    for node in ast.walk(ast.parse(f.read())):
        if isinstance(node, ast.Dict) and \
                not any(isinstance(child, ast.Call) for child in ast.walk(node)):
            d = eval(compile(ast.Expression(body=node), '', 'eval'))
            break
    else:
        print('No valid dict found.')

Given your sample input, d would become:

{'EMS': 1, 'ESC': 2, 'HVAC': 3, 'IC': 4, 'ICU': 5, 'IS': 6, 'ITM': 7, 'MBFM': 8, 'PKE': 9, 'RPAS': 10, 'RVC': 11, 'SAS': 12, 'SRS': 13, 'TCU': 14, 'TPMS': 15, 'VCU': 16, 'BMS': 17, 'MCU': 18, 'OBC': 19}

score 0 · Answer 2 · answered Apr 24 '19 at 05:29

0

You need to iterate over both the keys and values:

with open('filename') as f:
    data = ast.literal_eval(f.read())
    print(data)
    for name, age in data.items():
        if age == search_age:
            print(name)

Also, that file looks like a valid JSON object, so you should probably use json.load over ast.literal_eval.

answered Apr 24 '19 at 05:29

gmds

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4
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i tried this i got File "C:\Python37-32\lib\ast.py", line 46, in literal_eval node_or_string = parse(node_or_string, mode='eval') File "C:\Python37-32\lib\ast.py", line 35, in parse return compile(source, filename, mode, PyCF_ONLY_AST) File "", line 1 d = {'EMS': 1, 'ESC': 2, 'HVAC': 3,'IC' : 4,'ICU' : 5,'IS' : 6,'ITM' : 7,'MBFM' : 8,'PKE' : 9,'RPAS' : 10,'RVC' : 11,'SAS' : 12,'SRS' : 13,'TCU' : 14,'TPMS' : 15,'VCU' : 16,'BMS' : 17,'MCU' :18,'OBC' :19} ^ SyntaxError: invalid syntax – Tejesh Reddy Apr 24 '19 at 05:36
@TejeshReddy Your file itself is malformed. Take the `d = ` out. – gmds Apr 24 '19 at 05:38

score 0 · Answer 3 · answered Jul 14 '23 at 20:06

I like the accepted answer by @blhsing, but what if you want a dictionary by a specific variable name? At least that is what I was looking for.

Slight variation of @blhsing 's answer, using ast.Assign since that will have ast.Name and ast.Dict as its children.

import ast
from path lib import Path

def walk_file(dict_name, path):
    t = ast.parse(Path(path).read_text())
    return walk(dict_name, t)

def walk(dict_name, t):
    for node in ast.walk(t):
        if (
            isinstance(node, ast.Assign)
            and isinstance(node.value, ast.Dict)
            and node.targets[0].__dict__.get("id") == dict_name
        ):
            if not any(
                isinstance(child, ast.Call) for child in ast.walk(node)
            ):
                value = ast.literal_eval(node.value)
                return value
            else:
                print("uh oh, callables found!")
    else:
        print("No valid dict found.")

So for example,

blah = """
    d1 = {"hi": 2}
    def foo():
        d2 = {"hmm": {"interesting": [1, 2]}}
    
    d3 = {"sure": "great"}    
"""

t = ast.parse(blah)
for name in ["d1", "d2", "d3"]:
    print(name, walk(name, t))

d1 {'hi': 2}
d2 {'hmm': {'interesting': [1, 2]}}
d3 {'sure': 'great'}

How to read the dictionary from text file?

3 Answers3