如何用Perl解析文件的一部分？

Question

我是Perl的全新手，但是我听说它对于解析文件非常好，所以我想过给它一个旋转。

我有了下面的示例信息的文本文件：

High school is used in some 
parts of the world, particularly in 
Scotland, North America and Oceania to 
describe an institution that provides 
all or part of secondary education. 
The term "high school" originated in 
Scotland with the world's oldest being 
the Royal High School (Edinburgh) in 
1505. 

The Royal High School was used as a 
model for the first public high school 
in the United States, the English High 
School founded in Boston, 
Massachusetts, in 1821. The precise 
stage of schooling provided by a high 
school differs from country to 
country, and may vary within the same 
jurisdiction. In all of New Zealand 
and Malaysia along with parts of 
Australia and Canada, high school is 
synonymous with secondary school, and 
encompasses the entire secondary stage 
of education. 

====================================== 
Grade1 87.43% 
Grade2 84.30% 
Grade3 83.00% 
===================================== 

我想分析该文件，并只获得数字信息。我 看着正则表达式，我想我会使用类似

if (m/^%/) { 
    do something 
} 
else { 
    skip the line 
} 

但是，我真正想要做的是保持对 左侧履带的变量，并存储在该变量的数值。所以，在解析文件 后，我真的希望有以下变量 将％值存储在它们中。原因是，我想要 创建不同等级的饼图/条形图。

Grade1 = 87.43 Grade2 = 84.30

...

难道你会建议我应该看什么方法呢？

Answer 1

你需要一个正则表达式。类似以下内容应该可以工作

while (<>) { 
    /(Grade[0-9]+)\s*([0-9]+\.[0-9]+)/; 
    $op{$1} = $2; 
} 

作为过滤器。 op散列将存储等级名称和分数。这比自动实例化变量更可取。

Answer 2

创建动态变量名称可能不会帮助您制作图表;使用数组几乎肯定是一个更好的主意。

但是，如果你真的认为你想这样做：

while (my $line = <$your_infile_handler>){ 
    if ($line =~ m/(.*) = ([0-9.]*)){ 
     $$1 = $2; 
    } 
} 

应该做到这一点。

Answer 3

你想使用散列。像这样的应该做的伎俩：

my %grades =(); # this is a hash 
open(my $fh, "grade_file.txt") or die $!; 
while(my $line = <$fh>) { 
    if(my($name, $grade) = $line =~ /^(Grade\d+)\s(\d+\.\d+\%)) { 
     $grades{$name} = $grade; 
    } 
} 
close($fh); 

你的%grades哈希将包含名称和成绩对。 （访问它像my $value = $grades{'Grade1'}

也只有一个音符。这种语言被称为“Perl的”，而不是“PERL”。很多人在Perl社区生气吧:-)

Answer 4

如果你能保证你的兴趣点两个嵌套=秒（而没有奇数在给定文件中的这些分界线），触发器运营商这里是一个方便的事情之间：

use strict; # These two pragmas go a long, ... 
use warnings; # ... long way in helping you code better 

my %scores; # Create a hash of scores 

while (<>) { # The diamond operator processes all files ... 
       # ... supplied at command-line, line-by-line 

    next unless /^=+$/ .. /^=+$/; # The flip-flop operator used ... 
            # ... to filter out only 'grades' 

    my ($name, $grade) = split; # This usage of split will break ... 
            # ... the current line into an array  

    $scores{$name} = $grade;  # Associate grade with name 
} 

Answer 5

为例见Zaid's answer使用触发器操作符（这是我会推荐的）。 - 感谢您的答复

#!/usr/bin/perl 

use strict; use warnings; 

my %grades; 
my $interesting; 

while (my $line = <DATA>) { 
    if (not $interesting and $line =~ /^=+\s*\z/) { 
     $interesting = 1; 
     next; 
    } 
    if ($interesting) { 
     if ($line =~ /^=+\s*$/) { 
      $interesting = 0; 
      next; 
     } 
     elsif (my ($name, $grade) = $line =~ /^(\w+)\s+(\d+\.\d+%)/) { 
      # Keep an array in case the same name occurs 
      # multiple times 
      push @{ $grades{$name} }, $grade; 
     } 
    } 
} 

use YAML; 
print Dump \%grades;