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

Question

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.

Answer 1

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 .

Answer 2

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

Answer 3

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