CODEWITHSUNDEEP
pythonvariables
Jamie
Jamie

Reputation: 29

How do you turn the content of two variables into one callable variable name in python?

I am trying to get a variable to get a string out of a list (which is a variable name), and then I want to call that variable.

There is a list which stores a lot of variable names, and some other variables.

    fruits = ["apple","orange","banana","blueberry"]

    apple = ["A red fruit","sort of ball"]
    orange = ["An orange fruit","a ball"]
    banana = ["A yellow fruit","a fruit"]
    blueberry = ["A blue fruit","a berry"]
    number = 3

I want to get the fruit from the list that I have the 'number' for:

    print(fruits[number])

That will output: banana

The output is the name of a pre-existing list variable, so how do I call an item from that list?

I tried doing this:

    print((fruits[number])[2])

Which I thought may come out like this:

    print(banana[2])

And output: a fruit

Thank you in advance for your help.

Upvotes: 1

Views: 316

Answers (3)

Juani Calle Machado
Juani Calle Machado

Reputation: 26

To use a variable like you want isn't a good idea. In this case, the best way to handle what you want to do is using a "dict". This is a native "key: value" python's data structure.

You can define the fruits and their descriptions like this:

fruits = {'banana': ['A yellow fruit', 'a fruit'],
          'orange': ['An orange fruit', 'a ball'],
          ...
          ...}

Then if you want to print the description of some fruit you should use its key:

fruit_to_print = 'banana'
print fruits[fruit_to_print]

When run this will output:

['A yellow fruit', 'a fruit']

If you want to get, for example, the first item of the description:

print fruits[fruit_to_print][0]

which will output:

A yellow fruit

Dictionaries are not intended to be an ordered structure, so you shouldn't call its values using an index, but if you're REALLY sure of what you're doing you can do this:

fruits = {'banana': ['A yellow fruit', 'a fruit'],
      'orange': ['An orange fruit', 'a ball']}
number = 1
desc_index = 0
# fruits.keys() returns an array of the key names.
description = fruits[fruits.keys()[number]][desc_index] 

print description

>>> A yellow fruit

Bear in mind that adding or removing an element can potentially change the index of every other element.

Another way is to create a class Fruit and have an array of Fruit(s):

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

fruit1 = Fruit('banana', ['A yellow fruit', 'a fruit'])
fruit2 = Fruit('orange', ['An orange fruit', 'a ball'])

fruits = []
fruits.append(fruit1)
fruits.append(fruit2)

fruit = 1
description = 0

print fruits[fruit].description[description]

An orange fruit

Upvotes: 1

campovski
campovski

Reputation: 3163

This is not possible. The closest you can get is by using dictionaries, which are basically maps from keys to values. In your case, a dictionary would look like this:

fruits = {
    "apple": ["A red fruit","sort of ball"],
    "orange" : ["An orange fruit","a ball"],
    "banana": ["A yellow fruit","a fruit"],
    "blueberry": ["A blue fruit","a berry"]
}

Now you can do something like print(fruits['banana'][1]) which will print a fruit since fruits is a dictionary, 'banana' is a key in this dictionary, and fruits[banana] is equal to ["A yellow fruit","a fruit"]. When you access element on index 1 of fruits['banana'], it returns second element of that list, since lists are 0-indexed in Python, and that is a string a fruit.

Upvotes: 3

ArthurG
ArthurG

Reputation: 345

What you want is called an associative array, in python these are called dictionaries.

fruitsDict = {}

fruitsDict["apple"] = ["A red fruit","sort of ball"]
fruitsDict["orange"] = ["An orange fruit","a ball"]
fruitsDict["banana"] = ["A yellow fruit","a fruit"]
fruitsDict["blueberry"] = ["A blue fruit","a berry"]

If you want to get the keys of the dictionary as strings you can use

for key, value in fruitsDict.items():
      print(key,value[1])

Output:

Apple sort of ball
Orange a ball
Banana a fruit
Blueberry a berry

Click here for a working example in tutorials point

Upvotes: 3

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