Python 3.6 - user input call class variable

Question

I'm very new to Python (and programming in general) so I apologize if I am asking the wrong question.

I want to create a tool for looking up data from a dictionary where the user inputs a string, and if the string matches a variable in the dictionary, the attributes of the variable are printed. I am having trouble finding a way to convert the string input into a pre-defined variable. Here is a summary of what I have so far:

class Fruit:
  def __init__(self, name, color):
    self.name = name
    self.color = color

banana = Fruit('banana', 'yellow')

fruit_choice = input("What fruit would you like to know about?")

From here, I have tried a variety of ways to have the input string ("banana") call the variable(banana) and then perform other methods defined under the class. Using a dictionary key doesn't work because I want to include multiple attributes rather than just 1.

"looking up data from a dictionary" Well, where is said dictionary? "Using a dictionary key doesn't work because I want to include multiple attributes" You only want to store a single Fruit instance, no? — Aran-Fey
– Aran-Fey, Commented Apr 27, 2018 at 15:26
I did not include a dictionary in my example for the sake of keeping it simple — Dillon Lashley
– Dillon Lashley, Commented Apr 27, 2018 at 16:28

user3483203 · Accepted Answer · 2018-04-27 15:38:34Z

1

If you use a dictionary where the key is the name of the fruit, and the value is your Fruit instance, you could simply look up the values, and override __str__ with whatever you want the fruit description to be:

class Fruit:
  def __init__(self, name, color):
    self.name = name
    self.color = color

  def __str__(self):
    return '{}s are {}'.format(self.name, self.color)

dct = {}
dct['banana'] = Fruit('banana', 'yellow')

Now you can use your current method to find a fruit's attributes:

In [20]: ask = input('What fruit would you like to know about? ')
What fruit would you like to know about? banana

In [21]: dct.get(ask, 'Fruit not found')
Out[21]: bananas are yellow

This will also handle cases where a fruit is not in your dictionary:

In [23]: dct.get('apple', 'Fruit not found')
Out[23]: 'Fruit not found'

edited Apr 27, 2018 at 15:38

answered Apr 27, 2018 at 15:33

user3483203

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Comments

NBlaine · Accepted Answer · 2018-04-27 15:37:15Z

0

Here's mine:

class Fruit:
  def __init__(self, name, color, price):
    self.name = name
    self.color = color
    self.price = price
  def __str__(self):
    return "name: "+self.name+" color: "+self.color+" price: $"+str(self.price)

dict_of_fruits = {}
banana = Fruit('banana', 'yellow', 3)
apple = Fruit('apple', 'red', 2)

dict_of_fruits[banana.name] = banana
dict_of_fruits[apple.name] = apple


fruit_choice = input("What fruit would you like to know about?")

if fruit_choice in dict_of_fruits:
  print("Here are the attr. of ",fruit_choice,': ',dict_of_fruits[fruit_choice])
else:
  print("Sorry I could not find ",fruit_choice," in my records")

I included a __str__() method to make the print a little nicer, as well as a new price property since you mentioned there were more than 2 attr's

Output:

What fruit would you like to know about? banana
Here are the attr. of  banana :  name: banana color: yellow price: $3

answered Apr 27, 2018 at 15:37

NBlaine

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1 Comment

Dillon Lashley Over a year ago

Thank you! This is very helpful. Would the variable fruit_choice then be equivalent to the banana variable, in such a way that I could use other Fruit defined methods using fruit_choice.method() ?

Beat Bolli · Accepted Answer · 2018-04-27 15:29:38Z

0

You should still use a lookup dictionary. Its values may be another dict that holds each fruit's attributes, or a Fruit object.

answered Apr 27, 2018 at 15:29

Beat Bolli

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Comments

shahaf · Accepted Answer · 2018-04-27 15:32:02Z

0

you can use something like that, this only a draft to show the approach

class Fruit:
  def __init__(self, name, color):
    self.name = name
    self.color = color

  def __str__(self):
    return "{} : {}".format(self.name, self.color)

fruit_dict = dict()
banana = Fruit('banana', 'yellow')
fruit_dict.update({banana.name : banana})

fruit_choice = input("What fruit would you like to know about?")
user_fruit = fruit_dict.get(fruit_choice)
if user_fruit is not None:
    print(user_fruit)

output (if input was banana)

banana : yellow

answered Apr 27, 2018 at 15:32

shahaf

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