CODEWITHSUNDEEP
pythonpython-3.xdictionary
Bradley D. Freeman-Bain
Bradley D. Freeman-Bain

Reputation: 359

Verify string exists as key or value in Python dictionary?

I'm building a scraper/crawler for linux directories. in essence the program will take users input for a file type to scrape for (which is where my question comes in)

I'm storing acceptable file extension types in a dictionary w/ nested lists for example:

file_types = {'images': ['png', 'jpg', 'jpeg', 'gif', 'bmp'], 'text': ['txt', 'doc', 'pdf']}

To give the user which options they have to choose from I use this for loop:

for k, v in file_types.items():
    print(k, v)

Which prints the dictionary in this format:

audio ['mp3', 'mpa', 'wpi', 'wav', 'wpi']

text ['txt', 'doc', 'pdf']

video ['mp4', 'avi', '3g2', '3gp', 'mkv', 'm4v', 'mov', 'mpg', 'wmv', 'flv']

images ['png', 'jpg', 'jpeg', 'gif', 'bmp']

Now if I do:

scrape_for = input("Please enter either the type of file, or the extension you would like to scrape for: \n")

how can I validate the users input exists in my dictionary file_types as either a key OR a value (I say key OR value so if the user inputs 'images' I can use the values of the key images)

Upvotes: 1

Views: 132

Answers (2)

RinkyPinku
RinkyPinku

Reputation: 410

Using Python's cool list comprehension make a flat list of extensions

list_of_extensions = [ item \
    for extensionList in file_types.values() \
    for item in extensionList
]

Now use idiomatic Python construct item in list_var, which evaluates to True if the item is present in that list, and the or.

if scrape_for in file_types or scrape_for in list_of_extensions:
    # do something
else:
    print("Unsupported file type: " + scrape_for)

Note: using the in operator on dict name is equivalent (in effect) to scrape_for in file_types.keys()

Upvotes: 0

zwer
zwer

Reputation: 25829

I'd first flatten the extensions list into a set so you don't have to loop through it later on and can do quick on-the-spot lookups:

file_types = {'images': ['png', 'jpg', 'jpeg', 'gif', 'bmp'], 'text': ['txt', 'doc', 'pdf']}
file_extensions = set(sum(file_types.values(), []))

scrape_for = input("Enter the type / extension to scrape: ").lower()
if scrape_for not in file_types and scrape_for not in file_extensions:
    print("I don't support this type / extension!")

Upvotes: 3

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