Question

我该怎么做？

with open(r'C:\some_list.txt') as f:
    list = f.readlines()
for line in list:
    if line: #has more than x characters
        delete line

Answer 1

如果文件很小，最简单的方法是全部读取，过滤并全部写入。

with open(r'C:\some_list.txt')  as f:
    lines = f.readlines()

# Keep lines <= 10 chars long with a list comprehension
filtered_lines = [line for line in lines if len(line) > 10]

# Do what you like with the lines, e.g. write them out into another file:
with open(r'C:\filtered_list.txt', 'w') as f:
    for line in filtered_lines:
        f.write(line)

如果要将匹配的行流式传输到另一个文件中，那就更容易了：

with open(r'C:\some_list.txt') as in_file, open(r'C:\filtered_list.txt', 'w') as out_file:
    for line in in_file:
        if len(line) <= 10:
            out_file.write(line)

Answer 2

您可以逐行读取文件，如果通过了限制，则将该行写到新文件中（放弃其他行）。对于大文件，在内存使用方面如此高效：

with open('file_r.txt', 'r') as file_r, open('file_w.txt', 'w') as file_w:
    thresh = 3
    for line in file_r:
        if len(line) < thresh:
            file_w.write(line)

Answer 3

尝试（我以3为例）

with open(r'C:\some_list.txt')  as f:
    l = [i for i in f if len(i) > 3]

由于list是内置的，因此我将l重命名为list。

Answer 4

首先将行保存在列表中，通过逐个阅读不会删除这些行：

the_list = []
with open(r'C:\some_list.txt', "r") as f:
    for line in f:
        #print(len(line))
        if (len(line)) < 50:#here I used 50 charecters
            the_list.append(line)

然后将列表写入文件：

with open(r'C:\some_list.txt', 'w') as f:
    for line in the_list:
        f.write(line)

如果您不想使用列表或文件太大，请尝试：

with open(r'C:\some_list.txt', "r") as f, open('new.txt', 'a') as fw:
    for line in f:
        if (len(line)) < 50:
            fw.write(line)

根据需要替换output.txt。上面的代码将从some_list.txt中逐行读取，然后如果该行少于50个字符，则将其写入“ output.txt”中

Answer 5

相反，可以这样做：

# fname : file name
# x : number of characters or length
def delete_lines(fname = 'test.txt', x = 8):
    with open(fname, "r") as f:
        lines = f.readlines()
    with open(fname, "w") as f:
        for line in lines:
            if len(line) <= x:            
                f.write(line)

delete_lines()

当然，有更好的方法可以做到这一点。

如果行数超过x个字符，如何从文件中删除行

5 个答案: