如何用Python正则表达式提取字符串中的三种毫米产品尺寸？

算力阿峰

2026-5-21

Extracting Dimension Formats with Python Regex

Got it, let's solve this problem of pulling those three specific dimension formats from a string using Python's regular expressions. Here's a practical, easy-to-understand approach:

Step 1: Define the Regex Pattern

The key is to account for optional spaces around the x and between the second number and mm. The pattern below will match all three of your target formats:

\d+\s*x\s*\d+\s*mm

Let's break down each part:

\d+: Matches one or more digits (the numerical part of the dimensions)
\s*: Matches zero or more spaces (handles the optional spaces in your formats)
x: Matches the fixed character x (add re.IGNORECASE as a flag if you need to match uppercase X too)
mm: Matches the fixed unit suffix

Step 2: Python Code Implementation

Here's a complete example that extracts all matching dimensions from a sample string:

import re

# Sample input string with target formats and extra noise
input_str = "Check out our products: 20x20mm, 15 x 15 mm, 25x25 mm, plus a random 50mm part."

# Regex pattern to match all three dimension formats
dimension_pattern = r'\d+\s*x\s*\d+\s*mm'

# Extract all matches
extracted_dimensions = re.findall(dimension_pattern, input_str)

# Print the results
print("Extracted dimensions:", extracted_dimensions)
# Output: Extracted dimensions: ['20x20mm', '15 x 15 mm', '25x25 mm']

Optional: Extract Numerical Values Separately

If you want to get the individual numbers instead of the full dimension string, use capturing groups in the regex:

value_pattern = r'(\d+)\s*x\s*(\d+)\s*mm'
extracted_values = re.findall(value_pattern, input_str)

print("Extracted dimension values:", extracted_values)
# Output: Extracted dimension values: [('20', '20'), ('15', '15'), ('25', '25')]

Bonus: Strict Matching (Avoid Partial Hits)

If you need to avoid matching cases where mm is followed by other letters (like 20x20mmxyz), add a negative lookahead to ensure mm isn't followed by a word character: