CODEWITHSUNDEEP
pythonpython-3.xdictionarytext
Tejesh Reddy
Tejesh Reddy

Reputation: 51

How to read the dictionary from text file?

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)

Upvotes: 3

Views: 2360

Answers (3)

HeyWatchThis
HeyWatchThis

Reputation: 23563

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'}

Upvotes: 0

blhsing
blhsing

Reputation: 107124

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}

Upvotes: 4

gmds
gmds

Reputation: 19905

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.

Upvotes: 0

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