letters,space,digit,other=0,0,0,0

s=input("请输入一行字符：")

for i in range(len(s)):

if (s[i]>='a' and s[i]<='z') or (s[i]>='A' and s[i]<='Z'):

letters+=1

elif s[i]==' ':

space+=1

elif s[i]>='0' and s[i]<='9':

digit+=1

else:

other+=1

print("字母数：%d\n空格数：%d\n数字数：%d\n其他字符数：%d\n"%(letters,space,digit,other))

或

p=input('请输入一行字符:')

a,b,c,d=0,0,0,0

for i in p:

if((i<='Z' and i>='A') or (i<='z' and i>='a')):

a+=1

elif (i==' '):

b+=1

elif(i>='0' and i<='9'):

c+=1

else:

d+=1

print ('英文字母的个数为：'+str(a))

print ('空格的个数为：'+str(b))

print ('数字的个数为：'+str(c))

print ('其他字符的个数为：'+str(d))

或

letter,space,digit,other=0,0,0,0

s = input('input a string:')

for c in s:

if c.isalpha():

letter +=1

elif c.isspace():

space +=1

elif c.isdigit():

digit +=1

else:

other +=1

print("字母数：%d\n空格数：%d\n数字数：%d\n其他字符数：%d\n"%(letter,space,digit,other))