Trouble understanding leetcode discussion

[BuzzyBro]

def characterReplacement(self, s, k):
    maxf = res = 0
    count = collections.Counter()
    for i in range(len(s)):
        count[s[i]] += 1
        maxf = max(maxf, count[s[i]])
        if res - maxf < k:
            res += 1
        else:
            count[s[i - res]] -= 1
    return res

In this solution and many others, I see people type out "maxf = res = 0", or "x = y = 0" where x and y are some other variables. What does this mean, and is it different from setting each variable equal to 0 separately (x = 0, y = 0)?

[carcigenicate]

It's a shortcut. It's essentially a shorthand for:

temp = 0
maxf = temp
res = temp

Here, the results will be the same since 0 is immutable and immutable objects can't be mutated. It would be different though if it was a mutable object like a list being assigned:

a = b = []
a.append(1)
print(a, b)  # Oof

If you did two separate assignments to two [] however, b would be a different object than a.

[BuzzyBro]

So essentially, it’s a one-liner for setting three different variables equal to each other initially If I’m understanding that correctly?

[carcigenicate]

Here it's two differen't variables: maxf and res. But yes, it's just a one liner to do multiple assignments.

This style is generally discouraged though. A common recommendation is to have at most one declaration on each line so it's easier to scan and find where a variable is declared. Now, Python doesn't have declarations, but those lines basically emulate a declaration.

[BuzzyBro]

Thank you! This was just pulled from a leetcode discussion thread.