Python 正则表达式匹配特定长度的数字
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Regex to match digits of specific length
提问by MrGlass
I am looking to match a 15 digit number (as part of a larger regex string). Right now, I have
我希望匹配一个 15 位数字（作为更大的正则表达式字符串的一部分）。现在，我有
\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d
but I feel like there must be a cleaner way to do this.
但我觉得必须有一种更清洁的方法来做到这一点。
采纳答案by Marcelo Cantos
If your regex language is Perl-compatible: \d{15}.
如果您正则表达式语言是Perl兼容的：\d{15}。
It is difficult to say how handle the edges (so you don't accidentally grab extra digits) without knowing the outer context in which this snippet will be used. The definitive context-independent solution is this:
如果不知道将在其中使用此代码段的外部上下文，则很难说出如何处理边缘（这样您就不会意外获取额外的数字）。明确的独立于上下文的解决方案是这样的：
(?<!\d)\d{15}(?!\d)
You can put this in the middle of any regex and it will match (and only match) a sequence of exactly 15 digits. It is, however, quite awkward, and usually unnecessary. A simpler version that assumes non-alphanumeric boundaries (e.g., whitespace around the digits) is this:
你可以把它放在任何正则表达式的中间，它会匹配（并且只匹配）一个 15 位数字的序列。然而，这很尴尬，而且通常是不必要的。假设非字母数字边界（例如，数字周围的空格）的更简单版本是这样的：
\b\d{15}\b
But it won't work if the letters immediately precede or followed the sequence.
但是如果字母紧跟在序列之前或之后，它就不会起作用。
回答by paxdiablo
You can generally do ranges as follows:
您通常可以按如下方式执行范围：
\d{4,7}
which means a minimum of 4 and maximum of 7 digits. For your particular case, you can use the one-argument variant, \d{15}.
这意味着最少 4 位，最多 7 位数字。对于您的特定情况，您可以使用单参数变体\d{15}.
Both of these forms are supported in Python's regular expressions- look for the text {m,n}at that link.
Python 的正则表达式支持这两种形式-{m,n}在该链接中查找文本。
And keep in mind that \d{15}will match fifteen digits anywhere in the line, including a 400-digit number. If you want to ensure it only has the fifteen, you use something like:
请记住，这\d{15}将匹配行中任何位置的 15 位数字，包括 400 位数字。如果你想确保它只有十五个，你可以使用类似的东西：
^\d{15}$
which uses the start and end anchors, or
使用开始和结束锚点，或
^\D*\d{15}\D*$
which allows arbitrary non-digits on either side.
这允许任意一侧的非数字。
回答by FeLiX StEpHeN
There, are two ways i have, to limit numbers.
我有两种方法来限制数字。
using len,
使用len，
num = 1234
len(str(num)) <= 4
This output will be True / False.
此输出将为真/假。
using regular expression,
使用正则表达式，
import re
num = 12324
re.match(r'(?:(?<!\d)\d{4}(?!\d))', str(num))
The output will be regular expression object or None.
输出将是正则表达式对象或无。
