CODEWITHSUNDEEP
pythondictionarypep8try-except
RaphWork
RaphWork

Reputation: 395

Best way to check key value with dictionary in python

I have a dictionary and I want to add some index of the dictionary to variables.

I know that try except is more pythonic than else if. And I tried with try except and it's works perfectly but I have a lot of key to check and I can't figure out of which code is more pythonic

Here is my dictionary :

test = {"token":"eating", "stemm": "eat", "lemm": "eat", "pos":"VPP"}

def method_one(test):
    try:
        token = test["token"]
    except KeyError:
        token = None
    try:
        stemm = test["stemm"]
    except KeyError:
        stemm = None

def method_two(test):
    token = None
    stemm = None
    if "token" in test:
        token = test["token"]
    if "stemm" in test:
        stemm = test["stemm"]

I also tried one try except for all but when one failed, I can't know which one is failing so this is useless.

Any ideas of a third method? Or method one is the good one?

Upvotes: 0

Views: 2439

Answers (2)

Supreet Sethi
Supreet Sethi

Reputation: 1806

There is a direct lookup construct where create a set of valid keys that should exist in the dictionary

test = {"token":"eating", "stemm": "eat", "lemm": "eat", "pos":"VPP"}

def validate(d, valkeys): 
   keyset = set(test.keys())
if valkeys.issubset(keyset):
    return True
else:
     return False

if __name__ == "__main__":
   val = set(["token", "stemm"])
   inval = set(["token", "stemm", "st"])
   assert validate(test, val) == True
   assert validate(test, inval) == False

Upvotes: 0

han solo
han solo

Reputation: 6590

dict has get method that will return value or None. you could do item = dict.get(key) and this will return either the value(if the key exists) or None otherwise, which is what you are looking for it seems :)

>>> d = {'foo': 'bar'}
>>> d.get('foo')
'bar'
>>> item = d.get('fooo')
>>> item is None
True

Upvotes: 2

Related Questions