要遍历一个范围(如数组或表)，使用 for 循环。在数组上迭代时，当前数组元素存储在循环变量中。在遍历字典时， index 存储在循环变量中。
(in 内容测试)
for x in [5, 7, 11]: statement # Loop iterates 3 times with 'x' as 5, then 7 and finally 11. var dict = {"a": 0, "b": 1, "c": 2} for i in dict: print(dict[i]) for i in range(3): statement # Similar to [0, 1, 2] but does not allocate an array. for i in range(1,3): statement # Similar to [1, 2] but does not allocate an array. for i in range(2,8,2): statement # Similar to [2, 4, 6] but does not allocate an array. for c in "Hello": print(c) # Iterate through all characters in a String, print every letter on new line.