The other three lines are not unrelated. If you just take the first three lies (and the last one), it's fine:

    a = 0
    def f():
        print(a)
    f()

Maybe this is all obvious to you, but I'll bet you can't name any other language which behaves this way. Compare the original Python to JavaScript (or Lua, Perl, Tcl, Ruby, C, Scheme, Rust, Clojure, or ...):

    a = 0
    function f() {
        console.log(a)
        a = 1
    }
    f()
    f()

This one behaves how I think most people would initially expect the Python snippet to behave. First it prints 0, then it prints 1. (Of course JavaScript has it's flaws too...) If you don't believe me, ask your coworkers and friends what they think it does before running it.

My only real point is that Python conflates variable declaration and variable assignment in a way which initially seems like a friendly time-saver, but which ends up being pretty subtle and confusing until you've learned its quirks. All of that just to avoid declaring your variables (in some fictional version of Python):

    var a = 0
    def f():
        print(a)
        a = 1
    f()
    f()

Here it would be clear which are declarations + initializations, and which are only assignments. And for just the cost of typing the word "var", the compiler could tell you when you've made typos in your variable names. As an added bonus, you could get rid of the "global" and "nonlocal" keywords.