习题3：生成字符串a1b2c3d4e5f6g7h8i9j10
print("第一种方法")
s = " " #接收字符串
result = " " #输出结果字符串
for i in range(1,11):
s = chr(i+96) + str(i)
result += s
print(result)
print("第二种方法") #运用字符串拼接方法（“”.join()） 和列表 append 方法
result_list = [ ]
for i in range(97,107):
string = chr(i) + str(i-96)
result_list.append(string)
print("".join(result_list))
print("第三种方法") #运用推导列表进行编辑
>>> [ i for i in range(1,10)]
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> [ "%s%s"%(chr(i+96),i) for i in range(1,10)]
['a1', 'b2', 'c3', 'd4', 'e5', 'f6', 'g7', 'h8', 'i9']
>>> "".join( ["%s%s"%(chr(i+96),i) for i in range(1,10)] )
'a1b2c3d4e5f6g7h8i9'
习题7：判断一个输入的句子中有多少个字母
print("第一种方法")
word = input("请输入句子：")
words = [ ]
for i in word:
if i.isalpha():
words.append(i)
print(words)
print(len(words))
print("第二种方法")
strpun = ""
for i in word:
if i.isalpha():
strpun += "1"
print(strpun)
print(len(strpun))
习题8： 26个字母大小写成对打印，例如：Aa,Bb....
print("第一种方法")
for i in range( 65 , 91 ):
print( chr(i) + chr(i+32) + "," , end = "" )
print("第二种方法")
s = ""
for i in range ( 65 , 91 ):
s += chr(i) + chr(i+32) + ","
print(s)
print("第三种方法")
result = ""
for i in range( 65 , 91 ):
result += chr(i) + chr(i+32) + " "
results = result.split()
print( result )
print( results )
