在 Python 中迭代和比较未知数量的输入

Question

The following snippet takes two arguments, compares the values contained therein and prints any matches.

from sys import argv

print(set(argv[1]) & set(argv[2]))
#Output: python multicompare.py man fan
#{'n', 'a'}

How would one adapt this to deal with an unknown and potentially unlimited (or very large) amount of arguments? I tried iterating over the arguments and passing them to a function, but without having a known amount of arguments, how can I call set() against them all and reference them? What's expected:

#Output: python3 multicompare.py man fan dan tan han
# {'n', 'a'}
#Output: python3 multicompare.py man fan dan can fin tin mountain happen trappen
# {'n'} 

Answer 1

You can iterate over sys.argv and use &= operator. If you call this with arguments man fan dan can fin tin mountain happen trappen :

import sys

s = set(sys.argv[1])

for a in sys.argv[2:]:
    s &= set(a)

print(s)

Then it prints:

{'n'}

Answer 2

Using the intersection method of set s, you don't actually need to convert the arguments to sets (well, that is except one).

the non-operator version[s] of ... intersection() ... method[s] will accept any iterable as an argument. In contrast, their operator based counterparts require their arguments to be sets.

So you could do something like:

import sys

print(set(sys.argv[1]).intersection(*sys.argv[2:]))