What make function with huge list so slow

[Windson Yang]

'I'm just running them in succession and seeing how long they'. The full
code looks like this, this is only an example.py here. and I run 'time
python3 example.py' for each function.

    def fib_dp(n):
        dp = [0] * (n+1)
        if n <= 1:
            return n
        dp[0], dp[1] = 0, 1
        for i in range(2, n+1):
            dp[i] = dp[i-1] + dp[i-2]
        return dp[-1]

    def fib_dp2(n):
        # add dp here just for calculating memory allocation time
        dp = [0] * (n+1)
        if n <= 1:
            return n
        pre, now = 0, 1
        for i in range(2, (n+1)):
            pre, now = now, pre+now
        return now


    # run the function only once
    # fib_dp(400000) # took more than 60s
    # fib_dp2(400000) # took about 2s