Python 字典、列表操作及求和示例

1. 打印字典键值对

d = {'a': 'x', 'b': 'y', 'c': 'z'}

for key, value in d.items():
    print(key, value)

输出： a x b y c z

2. 在列表中插入元素

cities = ['beijing', 'shanghai', 'guangzhou', 'chongqin', 'shenzhen']
cities.insert(4, 'nanchang')
cities.insert(0, 'yunnan')

print(cities)

输出： ['yunnan', 'beijing', 'shanghai', 'guangzhou', 'nanchang', 'chongqin', 'shenzhen']

3. 求 1-2+3-4+5 ... 99 的所有数的和

sum = 0
for i in range(1, 100):
    if i % 2 == 0:
        sum -= i
    else:
        sum += i

print(sum)

输出： 50

4. 求 1!+2!+3!+4!+5!的和

sum = 0
for i in range(1, 6):
    fact = 1
    for j in range(1, i+1):
        fact *= j
    sum += fact

print(sum)

输出： 153