Python：如何提取指定标识符前的7个字符？

Got it, let's sort this out for you. Your current code grabs everything before the "Type of Occurrence" identifier, but we just need the last 7 characters of that prefix. Here are two straightforward ways to fix this:

Option 1: Improve Your Existing Split Approach #

You can keep using split() to get the full prefix, then slice the last 7 characters from it. This builds on the code you already have and keeps things simple:

A = "12/07/2019 11 : 00Type of Occurrence"
# Get all content before the identifier
full_prefix = A.split('Type of Occurrence', 1)[0]
# Extract the last 7 characters of the prefix
target_substring = full_prefix[-7:]
# Apply your existing formatting rules
print(target_substring.replace('.', '').upper())

This will output exactly 11 : 00 as you need. For edge cases where the prefix might be shorter than 7 characters, add a quick check to avoid errors:

full_prefix = A.split('Type of Occurrence', 1)[0]
if len(full_prefix) >= 7:
    target_substring = full_prefix[-7:]
else:
    target_substring = full_prefix  # Or handle this scenario based on your needs

Option 2: Use Regular Expressions for Precise Matching #

If you prefer a one-step solution, regex lets you directly capture the 7 characters right before your identifier:

import re
A = "12/07/2019 11 : 00Type of Occurrence"
# Capture exactly 7 characters immediately preceding the identifier
match = re.search(r'(.{7})Type of Occurrence', A)
if match:
    target_substring = match.group(1).replace('.', '').upper()
    print(target_substring)

The regex pattern (.{7}) captures any 7 characters, and Type of Occurrence anchors this capture right before your target identifier. This is ideal if you want to skip handling the full prefix entirely.

内容的提问来源于stack exchange，提问作者Mohannad