\\n 在函数的 return 语句中打印 \\n 而不是 python 中的新行

Question

Consider the below python code.I am very new to python.Please help me with this. this function returns '\\n56' but i need --new line-- 56

def fun_ret(num):
    return '\n'+str(num)
if __name__=='__main__':
    a=fun_ret(56)

I have gone through similar posts but it was all about print statement

Actual scenario is to pass the doctest of method str in a class.

def __str__(self):
    """(Maze)-->str
    The parameter represents a maze. Return a string representation of the maze 
    >>> maze=Maze([['#', '#', '#', '#', '#', '#', '#'],['#', 'J', '.', '.', 'P', '.', '#'], ['#', '.', '#', '#', '#', '.', '#'],['#', '.', '.', '@', '#', '.', '#'],['#', '@', '#', '.', '@', '.', '#'], ['#', '#', '#', '#', '#', '#', '#']], Rat('J', 1, 1),Rat('P', 1, 4))
    >>> str(maze)
    "#######
    #J..P.#
    #.###.#
    #..@#.#
    #@#.@.#
    #######
    J at (1, 1) ate 0 sprouts.
    P at (1, 4) ate 0 sprouts."
    """
    result=''
    for outer_list in self.maze_content:
        for inner_list in outer_list:
            result +='{0}'.format(str(inner_list))
        result+='\n'
    result += '\n'+'{0} at ({1}, {2}) ate {3} sprouts.'.format(self.rat_1.symbol,self.rat_1.row,self.rat_1.col,self.rat_1.num_sprouts_eaten)
    result += '\n'+('{0} at ({1}, {2}) ate {3} sprouts.'.format(self.rat_2.symbol,self.rat_2.row,self.rat_2.col,self.rat_2.num_sprouts_eaten))
    return result


if __name__=='__main__':
    import doctest
    doctest.testmod()

Answer 1

Are you working in a line-oriented command shell? If so, I can see your confusion. A typical command shell has a special routine for simply displaying a variable value, one that does not convert output formatting characters. For instance, the default Python interactive shell gives us this:

>>> def fun_ret(num):
...     return '\n'+str(num)
... 
>>> a=fun_ret(56)
>>> a
'\n56'
>>> print(a)

56
>>> 

Note the difference: the simple a command carefully displays the string value of the variable, expanding the visual short-hand for various control characters. The print command applies the standard formatter, which is where the \\n character is turned into an actual "new line" operation.

Does that help clear up the problem?

Answer 2

I know this is a really old question at this point but I found it while trying to solve a similar problem myself (I was doing a challenge in a course I was taking in which I had to print a string containing multiple lines out of a dictionary of strings). So, since some of the comments lead me to the answer, I'd like to share it here in case someone else has the same problem later.

Instead of returning, in OP's case, just the string:

def fun_ret(num):
    return '\n'+str(num)

you can return a print statement, like so:

def fun_ret(num):
    return print('\n'+str(num))

This wouldn't necessarily work if you potentially need to return that function into just a variable somewhere, in which case you'd probably be better off calling it in a print statement:

print(fun_ret(num)) 

instead.

I'm not sure if this will help with the actual situation specified by OP (pretty new to Python myself), but it will cause the function call to print a new line, rather than just return the value, if that's what someone needs for their use case.