username = input('username: ')
print('welcome', username) # print各项间默认以空格作为分隔符
print('welcome ' + username) # 注意引号内最后的空格
username = input('username: ')
print('welcome', username)
print('welcome ' + username)
username = input('username: ')
print('welcome', username) # print各项间默认以空格作为分隔符
print('welcome ' + username) # 注意引号内最后的空格
username = input('username: ')
print('welcome', username)
print('welcome ' + username)