每次调用file.write()时,我都想在字符串中添加换行符。在Python中最简单的方法是什么?


当前回答

我真的不想每次都输入\n, @matthause的答案似乎不适合我,所以我创建了自己的类

class File():

    def __init__(self, name, mode='w'):
        self.f = open(name, mode, buffering=1)
        
    def write(self, string, newline=True):
        if newline:
            self.f.write(string + '\n')
        else:
            self.f.write(string)

这就是它的实现

f = File('console.log')

f.write('This is on the first line')
f.write('This is on the second line', newline=False)
f.write('This is still on the second line')
f.write('This is on the third line')

这应该在日志文件中显示为

This is on the first line
This is on the second lineThis is still on the second line
This is on the third line

其他回答

你可以这样做:

file.write(your_string + '\n')

正如另一个答案所建议的,但为什么在可以调用文件时使用字符串连接(缓慢,容易出错)。写两次:

file.write(your_string)
file.write("\n")

注意,写操作是被缓冲的,所以两者是一样的。

如果你大量使用它(写了很多行),你可以子类化'file':

class cfile(file):
    #subclass file to have a more convienient use of writeline
    def __init__(self, name, mode = 'r'):
        self = file.__init__(self, name, mode)

    def wl(self, string):
        self.writelines(string + '\n')

现在它提供了一个额外的函数wl来做你想要的:

with cfile('filename.txt', 'w') as fid:
    fid.wl('appends newline charachter')
    fid.wl('is written on a new line')

也许我遗漏了一些东西,比如不同的换行符(\n, \r,…),或者最后一行也以换行符结束,但这对我来说是有效的。

你可以在需要这种行为的特定地方装饰方法write:

#Changed behavior is localized to single place.
with open('test1.txt', 'w') as file:    
    def decorate_with_new_line(method):
        def decorated(text):
            method(f'{text}\n')
        return decorated
    file.write = decorate_with_new_line(file.write)
    
    file.write('This will be on line 1')
    file.write('This will be on line 2')
    file.write('This will be on line 3')

#Standard behavior is not affected. No class was modified.
with open('test2.txt', 'w') as file:
        
    file.write('This will be on line 1')
    file.write('This will be on line 1')
    file.write('This will be on line 1')  

你可以使用:

file.write(your_string + '\n')

除非写入二进制文件,否则使用打印。下面的例子很适合格式化csv文件:

def write_row(file_, *columns):
    print(*columns, sep='\t', end='\n', file=file_)

用法:

PHI = 45
with open('file.csv', 'a+') as f:
    write_row(f, 'header', 'phi:', PHI, 'serie no. 2')
    write_row(f)  # additional empty line
    write_row(f, data[0], data[1])

您还可以使用partial作为一种更python化的方式来创建这种包装器。在下面的例子中,用预定义的kwargs打印行。

from functools import partial


with open('file.csv', 'a+') as f:
    row = partial(print, sep='\t', end='\n', file=f)

    row('header', 'phi:', PHI, 'serie no. 2', end='\n\n')
    row(data[0], data[1])

注:

打印文档 “{},{}”。format(1, 'the_second') - https://pyformat.info/, PEP-3101 '\t' -制表符 函数定义中的*列-将任意数量的参数分派到列表-参见关于*args和**kwargs的问题