如何使用 glob 读取具有数字名称的有限文件集? [英] How to use glob to read limited set of files with numeric names?

问题描述

如何使用 glob 只读取有限的文件集?

我在同一目录中有名为 50 到 20000 数字的 json 文件(例如 50.json,51.json,52.json...19999.json,20000.json).我只想读取编号为 15000 到 18000 的文件.

为此，我使用了一个 glob，如下所示，但每次我尝试过滤数字时它都会生成一个空列表.我已尽力点击此链接(https://docs.python.org/2/library/glob.html)，但我不确定我做错了什么.

<预><代码>>>>目录 = "/Users/Chris/Dropbox">>>read_files = glob.glob(directory+"/[15000-18000].*")>>>打印 read_files[]

另外，如果我想要任何大于 18000 的文件怎么办?

解决方案

您使用的 glob 语法不正确；[..] 序列对每个字符起作用.以下 glob 将正确匹配您的文件:

'1[5-8][0-9][0-9][0-9].*'

在幕后，glob 使用 fnmatch 将模式转换为正则表达式.您的模式转换为:

<预><代码>>>>导入 fnmatch>>>fnmatch.translate('[15000-18000].*')'[15000-18000]\..*\Z(?ms)'

匹配.之前的1个字符，一个0，1，5 或 8.没有别的.

glob 模式非常有限；匹配数字范围并不容易；您必须为范围创建单独 glob，例如 (glob('1[8-9][0-9][0-9][0-9]')+ glob('2[0-9][0-9][0-9][0-9]') 等).

改为自己过滤:

directory = "/Users/Chris/Dropbox"对于 os.listdir(directory) 中的文件名:基本名称，ext = os.path.splitext(文件名)如果 ext != '.json':继续尝试:数字 = int(basename)除了值错误:continue # 不是数字如果 18000 <= 数字 <= 19000:# 处理文件文件名 = os.path.join(目录，文件名)

How to use glob to only read limited set of files?

I have json files named numbers from 50 to 20000 (e.g. 50.json,51.json,52.json...19999.json,20000.json) within the same directory. I want to read only the files numbered from 15000 to 18000.

To do so I'm using a glob, as shown below, but it generates an empty list every time I try to filter out for the numbers. I've tried my best to follow this link (https://docs.python.org/2/library/glob.html), but I'm not sure what I'm doing wrong.

>>> directory = "/Users/Chris/Dropbox"
>>> read_files = glob.glob(directory+"/[15000-18000].*")
>>> print read_files
[]

Also, what if I wanted files with any number greater than 18000?

解决方案

You are using the glob syntax incorrectly; the [..] sequence works per character. The following glob would match your files correctly instead:

'1[5-8][0-9][0-9][0-9].*'

Under the covers, glob uses fnmatch which translates the pattern to a regular expression. Your pattern translates to:

>>> import fnmatch
>>> fnmatch.translate('[15000-18000].*')
'[15000-18000]\..*\Z(?ms)'

which matches 1 character before the ., a 0, 1, 5 or 8. Nothing else.

glob patterns are quite limited; matching numeric ranges is not easy with it; you'd have to create separate globs for ranges, for example (glob('1[8-9][0-9][0-9][0-9]') + glob('2[0-9][0-9][0-9][0-9]'), etc.).

Do your own filtering instead:

directory = "/Users/Chris/Dropbox"

for filename in os.listdir(directory):
    basename, ext = os.path.splitext(filename)
    if ext != '.json':
        continue
    try:
        number = int(basename)
    except ValueError:
        continue  # not numeric
    if 18000 <= number <= 19000:
        # process file
        filename = os.path.join(directory, filename)

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