如何使用Regex按1B、2E、1D、4E规则对数值字符串分组？

Got it, let's tackle this grouping problem step by step. Based on your example, the grouping logic is clear: we need to split the comma-separated string into four ordered groups:

1. 1B: All items ending with B
2. 2E: All E-ending items that appear before any D items
3. 1D: All items ending with D
4. 4E: All remaining E-ending items that come after the D items

Here are two practical solutions you can use:

Method 1: String Splitting + Iterative Grouping (Flexible & Easy to Maintain) #

This approach is straightforward and works even if the number of items in each group varies (as long as the order of B→E→D→E stays consistent).

Steps: #

1. Split the input string into a list of individual items using , as the delimiter.
2. Iterate through the list, routing each item to the correct group based on its suffix and the current group we're collecting.

Code Example (Python): #

s1 = "7.51B, 8.01B, 7.02E, 7.52E, 8.02E, 7.01D, 7.51D, 8.01D, 8.54E, 9.04E, 9.54E, 10.04E, 10.54E, 11.04E"

# Split and clean up the items
items = [item.strip() for item in s1.split(',')]

# Initialize empty groups
group_1b = []
group_2e = []
group_1d = []
group_4e = []

# Track which group we're currently adding items to
current_group = group_1b

for item in items:
    if current_group == group_1b:
        if item.endswith('B'):
            group_1b.append(item)
        else:
            # Switch to 2E group and add the current item
            group_2e.append(item)
            current_group = group_2e
    elif current_group == group_2e:
        if item.endswith('E'):
            group_2e.append(item)
        else:
            # Switch to 1D group and add the current item
            group_1d.append(item)
            current_group = group_1d
    elif current_group == group_1d:
        if item.endswith('D'):
            group_1d.append(item)
        else:
            # Switch to 4E group and add the current item
            group_4e.append(item)
            current_group = group_4e
    else:
        # Add all remaining items to 4E group
        group_4e.append(item)

# Format the output as requested
formatted_output = (
    f"1B - {', '.join(group_1b)};\n"
    f"2E - {', '.join(group_2e)};\n"
    f"1D - {', '.join(group_1d)};\n"
    f"4E - {', '.join(group_4e)}"
)

print(formatted_output)

Method 2: Regular Expression Matching (For Fixed Input Format) #

If you know the input string will always follow the exact order of B→E→D→E with no unexpected variations, you can use a regex to directly capture each group in one go.

Regex Pattern Explanation: #

• (?:\d+\.\d+[BED], )*: Non-capturing group to match repeated items (e.g., 7.51B, )
• \d+\.\d+[BED]: Matches a single item (like 8.01B)
• Four capturing groups correspond to the four target groups.

Code Example (Python): #

import re

s1 = "7.51B, 8.01B, 7.02E, 7.52E, 8.02E, 7.01D, 7.51D, 8.01D, 8.54E, 9.04E, 9.54E, 10.04E, 10.54E, 11.04E"

# Regex pattern to capture all four groups
pattern = r'^((?:\d+\.\d+B, )*\d+\.\d+B), ((?:\d+\.\d+E, )*\d+\.\d+E), ((?:\d+\.\d+D, )*\d+\.\d+D), ((?:\d+\.\d+E, )*\d+\.\d+E)$'
match_result = re.match(pattern, s1)

if match_result:
    # Extract each captured group
    group_1b = match_result.group(1)
    group_2e = match_result.group(2)
    group_1d = match_result.group(3)
    group_4e = match_result.group(4)
    
    # Format and print the output
    formatted_output = (
        f"1B - {group_1b};\n"
        f"2E - {group_2e};\n"
        f"1D - {group_1d};\n"
        f"4E - {group_4e}"
    )
    print(formatted_output)
else:
    print("Input string doesn't match the expected format!")

Which Method to Choose? #

• Use Method 1 if you need flexibility (e.g., the number of items in each group might change, or you want to handle edge cases easily).
• Use Method 2 if your input format is strictly fixed and you prefer a more concise regex-based approach.

内容的提问来源于stack exchange，提问作者Sathya Narayana