# Dont need to understand
def is_float(s):
    '''(str) -> bool

    Return True iff the string represents a valid floating point number
    (i.e., it can be converted to float without problems)

    >>> is_float("3")
    True
    >>> is_float("-2.7")
    True
    >>> is_float("Two")
    False

    '''
    try:
        float(s)
        return True
    except:
        return False





#Given a PH value, output a message
ph_input = input("Enter PH value: ")
if(is_float(ph_input)):
    ph = float(ph_input)
    if(ph < 7.0):
        if(ph > 5.0):
            print("Your water is acidic, but you're probably okay")
        else:
            if(ph < 2):
                print("RUN!")
            else:
                print("That's pretty acidic, I wouldn't drink it")
    else:
        if(ph > 7.0):
            if(ph > 11):
                print("RUN!")
            else:
                print("That's pretty basic stuff")
        else:
            print("Your water is neutral.")
else:
    print("Not a valid PH!")







#A better approach

# if it's not a float, tell the user
if(is_float(ph_input)):
    ph = float(ph_input)
    # first deal with unrealistic ph levels
    if((ph > 11) or (ph < 2)):
        print("RUN!")
    # deal with anything over 7
    elif(ph > 7):
        print("That's pretty basic stuff")
    # deal with the case of it being exactly 7
    elif(ph == 7):
        print("Your water is neutral")
    # deal with anything over five (and since we're using an elif, we know
    # that it's below 7 at this point)
    elif(ph > 5):
        print("Your water is acidic, but you're probably okay")
    # if we reached this point, we know that the ph is 5 or lower
    else:
        print("That's pretty acidic, I wouldn't drink it")
else:
    print("Not a valid PH!")