import re
string = '\t \r\nFoo\t Fooo\t Dog\t Foo\t \r\n\r\n'
result = re.sub(
'^[\r\n\t]+|[\r\n\t]+$|([\r\n\t]+)',
lambda x: '|' if x.group(1) else '',
string
)
print(result)
aW1wb3J0IHJlCgpzdHJpbmcgPSAnXHQgXHJcbkZvb1x0IEZvb29cdCBEb2dcdCBGb29cdCBcclxuXHJcbicKcmVzdWx0ID0gcmUuc3ViKAogICAgJ15bXHJcblx0XSt8W1xyXG5cdF0rJHwoW1xyXG5cdF0rKScsCiAgICBsYW1iZGEgeDogJ3wnIGlmIHguZ3JvdXAoMSkgZWxzZSAnJywKICAgIHN0cmluZwopCnByaW50KHJlc3VsdCk=