Question

我需要检查正在使用的.csv文件是否以超过1条"\n"行结尾。如果发现多个空白行，则将其全部删除，但不包含一个空白行。

我的代码是：

import os
from pathlib import Path


def remove_blanks():
    dirname = os.path.dirname(os.path.abspath(__file__))
    path: Path = Path(os.path.join(dirname, "data.csv"))
    with open(path, "r+") as op:
        lines = op.readlines()
        for line in lines:
            if line == "\n":
                op.write(line.rstrip("\n"))

.csv文件类似于['01-01-2019,0,0,0\n', '18-05-2019,33,31,48\n', '\n', '\n', '\n']，我想要的输出是['01-01-2019,0,0,0\n', '18-05-2019,33,31,48\n', '\n']，但似乎无法删除任何行。

Answer 1

最简单的方法是跟踪空行，然后在编写 non 空行之前写一个。

pre = ""
for line in lines:
    if line == "\n":
        pre = line
    else:
        op.write(pre)
        op.write(line)
        pre = "\n"
op.write(pre)

这会将空行的任何序列减少为单个空行，并在写入非空行或文件末尾之前写入该单行。当pre为空字符串时，将其写为空操作。

如果要在文件中间保留多个空行，请在找到它们时在pre中建立空行序列，并在文件末尾仅写一个空行（而不是pre本身），如果pre不为空。

pre = ""
for line in lines:
    if line == "\n":
        pre += line
    else:
        op.write(pre)
        op.write(line)
        pre = ""
if pre:
    op.write("\n")

Answer 2

糟糕，切勿重写正在读取的文件：它可能无法正常工作，或充其量只会导致维护噩梦。

如果文件足够小以适合主内存，则代码中的这种轻微更改就足够了：

import os.path
from pathlib import Path


def remove_blanks():
    dirname = os.path.dirname(os.path.abspath(__file__))
    path: Path = Path(os.path.join(dirname, "data.csv"))
    with open(path, "r") as op:
        lines = op.readlines()  # read lines in memory
    with open(path("w") as op:  # re-write everything from the beginning
        flag = False     
        for line in lines:
            if line == "\n":
                if not flag:
                    op.write(line)
                flag = True
            else:
                op.write(line)
                # flag = False  # uncomment if you want to keep one blank line 
                                # per group of consecutive lines

Answer 3

您可以尝试使用Counter()。

import os
from pathlib import Path
from collections import Counter

def remove_blanks():
    dirname = os.path.dirname(os.path.abspath(__file__))
    path: Path = Path(os.path.join(dirname, "data.csv"))
    with open(path, "r+") as op:
        lines = op.readlines()
        for line in lines:
            count = Counter()
            # Add 1 for every time word appears in line
            for word in line:
                count[word] += 1
            # Change the number of newlines to 1
            if count['\n'] > 1:
                count['\n'] = 1
            # Returns list with the number of elements
            line = list(count.elements())

Answer 4

我设法用以下代码解决了这个问题：

import os
from pathlib import Path


def remove_blanks():
    dirname = os.path.dirname(os.path.abspath(__file__))
    path: Path = Path(os.path.join(dirname, "data.csv"))
    with open(path, "r") as op:
        lines = op.readlines()  # read lines in memory
    with open(path, "w") as op: # re-write everything from the beginning
        for line in lines:
            if line != "\n":
                op.write(line)
            else:
                continue

它可以删除多余的每一行，无论它在文件中的什么位置。

感谢所有试图帮助我的人！

如何从Python文件中删除“ \ n”行？

4 个答案: