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Convert a String representation of a Dictionary to a dictionary

python
dataframe
pandas
best-practices
Anton ShumikhinbyAnton Shumikhin·Feb 2, 2025
TLDR

The go-to function for converting a string dictionary to a Python dictionary is ast.literal_eval():

import ast string_dict = "{'key': 'value'}" real_dict = ast.literal_eval(string_dict) # The string has turned into a coat with real pockets now.

Safety is priority with this neat function. It steps up to safeguard against executing destructive code, unlike eval().

For converting JSON strings, where double quotes are a must, use the json.loads() function:

import json json_string = '{"key": "value"}' json_dict = json.loads(json_string) # That string is now more useful than my JSON degree.

This method is JSON-savvy, developed for speed and performance especially when dealing with large datasets.

ast.literal_eval() - secure and reliable

Consider ast.literal_eval() as your reliable partner when dealing with Python literals inside string representations. It excels in safely interpreting Python literals, and wouldn't trip on tuples, lists, dicts, booleans, or numbers.

import ast string_complex = "{'key': ['value1', 'value2'], 'key2': ('value3', 'value4')}" complex_dict = ast.literal_eval(string_complex) # This string went from 'useless' to 'useful' pretty fast, didn't it?

It ensures only Python literals are processed, reducing risks of running harmful code.

json.loads() - fast and efficient

When dealing with JSON data or large datasets, json.loads() is your knight in shining armour. Just remember to use double quotes around keys and values.

import json json_string = '{"key": ["value1", "value2"], "key2": ["value3", "value4"]}' json_dict = json.loads(json_string) # Who knew that JSON and Python make a good pair?

It's tailored for JSON, more suited for heavy-duty tasks than ast.literal_eval() but can only translate JSON-formatted strings.

Weapon of choice: ast.literal_eval() vs json.loads()

In the battlefield of string-to-dict conversion, always choose the right weapon. For security, ast.literal_eval() is your shield while json.loads() spearheads performance.

But remember, never wield the eval() weapon. Its lack of discretion in executing any code can invite security threats. Be smart, not sorry.

Real world drama - yaml.load()

In real-world scenarios, you may come across non-standard JSON strings. Fear not, with your armoury upgraded with PyYAML library, you're ready for the rescue.

import yaml yaml_string = "key: value" yaml_dict = yaml.safe_load(yaml_string) # The string has now earned its degree in Pythonology.

Note: Always use yaml.safe_load() for your safety. It's the secure avatar of yaml.load().

Time is Money - %timeit

In programming, especially with large datasets, time is a crucial factor. Benchmark your functions with %timeit to figure out which one is the silver bullet for your case.

%timeit json.loads(json_string) # 'Lightning' McQueen of JSON parsing %timeit ast.literal_eval(string_dict) # The 'Tortoise' but Secure Way

Mission Possible - Handling anomalies

Converting strings can be a deceitful maze. Be aware of these traps:

  • Strings with single quotes can make json.loads() trip. Do a replace to switch to double quotes whenever needed, but be careful not to wreck the string content.
  • Ill-formatted strings are bound to run into ValueError or JSONDecodeError roadblocks. Have right error handling to navigate safely.

The Trial Room - Test and Decide

When in dilemma, run a reality check. Use some elbow grease, experiment with various string formats, complexities and observe the outcomes. Real-life results sometimes reveal secrets that theory fails to.