(This is Python 2.7.10)

I am traversing through a list of sublists that like this:

for x in words:
    for subs in bigLsts:
        if x in subs:
            print() # Here, I want to print a different word in subs that is not the same word

bigLsts is a list of word lists formatted like this:

bigLsts = [["herro", "hewwo", "holas"], ["woah", "woahwa", "whatda"] ]

If x is in the subs, how can I print another word in the sublist that is not the same word as x? So, if x = "hewwo" how can I print either "herro" or "holas" but now "hewwo"

I have some solutions like generating a random number that does not include the index of that element, but solutions like that feel a bit clunky to me. Is there any cleaner solution?

CodePudding user response：

Generating a random number that is not the index of the element does not have to be clunky. One simple way to do it is to generate a number that is in the range [0, len(subs) - 2] and add one if the number is greater than or equal to the index you want to avoid. You can use the fact that python booleans are a subtype of integers to make the computation very simple:

ind = random.randrange(0, len(subs) - 1)
ind  = ind >= subs.index(x)
print(subs[ind])

That being said, you can use an even simpler formulation, courtesy of this unrelated answer:

min((i for i in subs if i != x), key=lambda x: random.random())

The idea is to take the element with the minimum uniformly randomly generated key. The generator automatically handles skipping the element you want to skip without doing an index lookup or ever mentioning indices at all.

CodePudding user response：

In your inner loop, you can consider using the following try statement (to replace the if x in subs):

from random import randrange
try:
     idx = subs.index(x)
     while (a := randrange(0, len(subs))) == idx:
          pass
     print(subs[a])
except ValueError:
     pass

The try clause tries to find the index in subs with corresponding element equal to the word x.

• In the event that x is not found, a ValueError is raised and we quietly ignore it.
• In the event that x is found, idx is assigned the corresponding index. Then, we assign a random integer in [0, len(subs) - 1] (i.e. the set of valid indices for subs) to a until a is not equal to idx. Once a is not equal to idx, we break out of the loop and print subs[a].

Drawing inspiration from @Mad Physicist, it would be better if the while statement were replaced with

if (a := randrange(0, len(subs) - 1)) >= idx:
     a  = 1

which assigns a to a random integer in [0, len(subs) - 1) and compares it against idx. In the event that a is greater than or equal to idx, a is incremented by 1.

Example Session

Suppose that

words = ["green", "eggs", "and", "ham", "hewwo", "woahwa"]
bigLsts = [['herro', 'hewwo', 'holas'], ['woah', 'woahwa', 'whatda']]

A session might yield output

herro
whatda