# 4，定义一个字符串str='abcdefghijklmnopqrstuvwxyz'，
# 在每个字符前面加上序号。比如‘1a2b3c.....26z’
print('first'.center(40,'='))
str1 = 'abcdefghijklmnopqrstuvwxyz'
list1 = []
for i in range(len(str1)):
connect = str(i+1)+str1[i]
list1.append(connect)
result = ''.join(list1)
print(result)
print('second'.center(40,'='))
str1 = 'abcdefghijklmnopqrstuvwxyz'
list2 = []
for i,m in enumerate(str1):
str2 = str(i+1)+m
list2.append(str2)
result = ''.join(list2)
print(result)
print('third'.center(40,'='))
str1 = 'abcdefghijklmnopqrstuvwxyz'
for i in str1:
result = str(str1.find(i) + 1) + i
print(result, end='')
