测试一个字符串是否包含Perl中的哈希键 [英] Test if a string contains the key of a hash in Perl

问题描述

我有一个字符串，并且想知道它是否包含散列键，如果是，我想打印散列值如下所示：

I have a string and want to tell if it contains the key of a hash and if it does I would like to print the value of the hash like so:

#!/usr/bin/perl -w

my %h = ( 'key1' => 'v1', 'key2' => 'v2', 'key3' => 'v3' );
my $str = "this is a string containing key1\n";
if ($str contains a key of %h){
    print the value of that key; #i.e v1
}

最好的方法是什么？ （最好足够简洁以便包含在if语句中）

Whats the best way to do this? (Preferably concise enough to contain in an if statement)

推荐答案

如果您必须搜索多个字符串，但只有一个不变散列，将散列键编译成正则表达式可能会更快，然后将该正则表达式应用于每个字符串。

If you have to search through multiple strings but have just the one unchanging hash, it might be faster to compile the hash keys into a regexp upfront, and then apply that regexp to each string.

my %h = ( 'key1' => 'v1', 'key2' => 'v2', 'key3' => 'v3' );
my $hash_keys = qr/${\ join('|', map quotemeta, keys %h) }/;

my @strings = (
   "this is a string containing key1\n",
   "another string containing key1\n",
   "this is a string containing key2\n",
   "but this does not\n",
);

foreach my $str (@strings) {
   print "$str\n" if $str =~ $hash_keys;
}

这篇关于测试一个字符串是否包含Perl中的哈希键的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！