Python学习笔记（3）range的用法

The Python range() function is just a shortcut for generating a list, so you can use ranges in all the same places you can use lists.

rang（）函数用于方便地产生一个表，用例：

range(6) # => [0,1,2,3,4,5]
range(1,6) # => [1,2,3,4,5]
range(1,6,3) # => [1,4]

三种使用方法：

1. range(stop)
2. range(start, stop)
3. range(start, stop, step)

In all cases, the range() function returns a list of numbers from start up to (but not including) stop. Each item increases by step.

如果缺省start 和step 则默认start=0，step=1

例（1）：

def my_function(x):
    for i in range(0, len(x)):
        x[i] = x[i] * 2
    return x

print my_function(range(3)) # Add your range between the parentheses!

结果：

[0, 2, 4]

例（2）：

n = [3, 5, 7]

def total(numbers):
    result=0
    for item in range(len(numbers)):
        result+=numbers[item]
    return result

print total(n)   

以上代码等价于：

n = [3, 5, 7]

def total(numbers):
    result=0
    for item in numbers:
        result+=numbers[item]
    return result

print total(n)   

结果：

15