04. 解决方案: For 循环

解决方案: 列表的总和 

def list_sum(input_list):
    sum = 0
    for element in input_list:
        sum += element
    return sum

#These test cases check that list_sum works correctly
test1 = list_sum([1, 2, 3])
print("expected result: 6, actual result: {}".format(test1))

test2 = list_sum([-1, 0, 1])
print("expected result: 0, actual result: {}".format(test2))

format 函数的说明可以参考 这里 。

解决方案: XML 标签计数器 

def tag_count(list1):
    count = 0
    for element in list1:
        if element[0] == '<' and element[-1] == '>':
            count += 1
    return count


# Test for the tag_count function:
list1 = ['<greeting>', 'Hello World!', '</greeting>']
count = tag_count(list1)
print("Expected result: 2, Actual result: {}".format(count))

解决方案：创建 HTML 列表 

def html_list(list_items):
    HTML_string = "<ul>\n"
    for item in list_items:
        HTML_string += "<li>{}</li>\n".format(item)
    HTML_string += "</ul>"
    return HTML_string

print(html_list(['First element', 'Second element', 'Third element']))

解决方案: Starbox

我们可以通过下面的训话来打印正确的行数： 

for _ in range(height-2):
        print("*" + " " * (width-2) + "*")

这个循环使用 range 作为一个简单的计数器，循环的主体部分执行了 height - 2 次。下划线 _ 是一个无关变量，因为我们在循环计数中对它的实际值并不感兴趣。

下面是完整解决方案： 

def starbox(width, height):
    """print a box made up of asterisks.

    width: width of box in characters, must be at least 2
    height: height of box in lines, must be at least 2
    """
    print("*" * width) #print top edge of box

    # print sides of box
    for _ in range(height-2):
        print("*" + " " * (width-2) + "*") 

    print("*" * width) #print bottom edge of box

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