来自builtins.py：
def print(self, *args, sep=' ', end='\n', file=None): # known special case of print
"""
print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False) Prints the values to a stream, or to sys.stdout by default.
Optional keyword arguments:
file: a file-like object (stream); defaults to the current sys.stdout.
sep: string inserted between values, default a space.
end: string appended after the last value, default a newline.
flush: whether to forcibly flush the stream.
"""
pass 使用1，练习sep的用法：
print("file\n","abc","bcd","fff\n","poi")
print("-------------")
print("file\n","abc","bcd","fff\n","poi",sep='')
print("-------------")
print("file\n","abc","bcd","fff\n","poi",sep=' ')
print("-------------")
其结果为：
file
abc bcd fff
poi
-------------
file
abcbcdfff
poi
-------------
file
abc bcd fff
poi
-------------
使用2，练习end的用法：
print("file\n","abc","fff",sep='#########\n',end='')
print("--------------------")
print("file\n","abc","fff",sep='#########\n',end='\n')
print("--------------------")
print("file\n","abc","fff",sep='#########\n')
print("--------------------")
其结果为：
file
#########
abc#########
fff--------------------
file
#########
abc#########
fff
--------------------
file
#########
abc#########
fff
--------------------
使用3,练习file的用法：
with open('abc.txt','w') as f:
print("file\n","abc","fff",sep='#########\n',end='',file=f)
其结果：
将输出写到了文件abc.txt。
abc.txt的内容如下：
file
#########
abc#########
fff
注意文件末行没有换行符