Lesson 39 of 55
9 mins readPython Capturing Groups ($1, $2) & Named Captures
In Plain English
Parentheses `(...)` in regular expressions capture matching substrings into the special read-only variables `$1`, `$2`, `$3`. Modern Perl also supports named captures via `(?<name>...)` stored in `%+`.
Deep Dive: How It Works
Numbered Captures ($1, $2, ...): Left-to-right based on opening parenthesis order.
List Context Captures: `my ($day, $month, $year) = ($date =~ /(\d{2})-(\d{2})-(\d{4})/);`.
Non-Capturing Groups (?:...): Groups expressions for quantifiers without saving variables.
Named Captures: `(?<user>\w+)` accessible via `$+{"user"}`.
Core Rules to Remember
$1, $2 Capture Variables: Auto-populated with substrings matched inside `(...)`.
List Context Extraction: Directly unpack captures into variables in a single step.
Live Interactive Example
Hit Run Code to see it liveExtracting Date and Domain Information
Python 3.12
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Output Console
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How it works: Numbered captures unpacked date components and URL segments cleanly.
Your Turn: Micro Challenge
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Micro Exercise
Capture Key-Value Pair
- Set `my $config = "timeout=30";`
- Extract key and value using `if ($config =~ /^(\w+)=(\d+)$/)` and print `"Key: $1, Val: $2\n"`.
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Sandbox Output
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