Master Python Regex: Extract Dates with One Powerful Pattern

Python Regex for Date Extraction

In this article we demonstrate how to construct a regular expression in Python that can match various date formats commonly used when writing exam dates, including 2018年6月7日, 2018/6/7, 2018-06-07, 2018-06 and plain year‑month strings.

We start with a very simple pattern and iteratively improve it while testing against several example strings.

Step 1 – Match any preceding text

The token .* matches any character sequence any number of times, allowing us to ignore the surrounding text such as "高考时间是".

Step 2 – Capture the year

\d{4}

matches exactly four digits, representing the year (e.g., 2018). It is followed by a character class [年/-] that accepts the Chinese character 年, a slash / or a hyphen -.

Step 3 – Capture the month

\d{1,2}

matches one or two digits for the month (e.g., 6 or 06). It is followed by [月/-] to accept 月, / or -.

Step 4 – Capture the optional day

The day part is similar: \d{1,2} for one or two digits, followed by 日 or the end of the string. Because some strings omit the day, we use an alternation with the end‑anchor $ to make the day optional.

Step 5 – Combine into a full pattern

Putting the pieces together, a robust pattern looks like:

pattern = r".*高考时间是.*?(\d{4})[年/-](\d{1,2})[月/-](\d{1,2})?日?"

This pattern successfully matches all six test strings shown below.

Testing results (illustrated in the images):

After the final adjustment, the pattern correctly matches all six different date representations, demonstrating the flexibility and power of regular expressions in Python.