练习

 #1-2+3-4+5.....+99=? 

count = 1
sum = 0
while count < 100:
    if count % 2 == 1:
        sum = sum + count
    else:
        sum = sum - count
    count += 1
print(sum)

 #统计字符串中的数字，连在一起的数字算1个

s = input('随便输入一串字母和数字混合的字符串>>>')#统计字符串中的数字，连在一起的数字算1个
l1 = len(s)
index = 0
count = 0
while index != l1-1:
    index += 1
    if s[index-1].isdigit():
        if s[index].isdigit():
            continue
        count += 1
if s[index].isdigit():
    count += 1
print(count)