# [Pushy], 8 bytes

Simple implementation of checking whether `len(set(list)) == len(list)-1`:

    LtvuL^=#

Explanation:

           \ Implicit: Put all input on stack
    Ltv    \ Get the stack length - 1, save in auxiliary stack
    u      \ Remove non-unique elements
    L      \ Get the new length
    ^=     \ Compare with the previously saved length
    #      \ Print result

This works as the length will only decrease by 1 if there was only exactly 1 non-distinct integer in the initial list.

[Try it online!][TIO-j8nhw74t]

[Pushy]: https://github.com/FTcode/Pushy
[TIO-j8nhw74t]: https://tio.run/##Kygtzqj8/9@npKzUJ85W@f///9GGOmY6xjomQGiuYxkLAA "Pushy – Try It Online"