方法一:
#a = input().split(" ")
#for i in a:
# if len(i) == 3:
# print(i)
方法二:
#a = [i for i in input().split() if len(i) == 3]
#print(' '.join(a))
方法三:
#import re
#a = input()
#b = re.findall(r' +[a-zA-Z]{3} ??', a)
#print(b)
def main():
lines = input()
list_line = lines.split(" ")
line = list()
for word in list_line:
if len(word) == 3:
line.append(word)
print (" ".join(line))
if __name__ == "__main__":
main()
import re
def main():
content = input('请输入字符串:')
new_content = re.findall(r'\w+', content)
for _ in new_content:
if len(_) == 3:
print(_)
if __name__ == "__main__":
main()