搜索和這種情況下更換模式

Question

我在尋找以下情況的解決方案：

原文：

= This is the first line = 
= This is the first line again 
== This is the second line == 
=== This is the third line === 
==== This is the forth line ==== 
==== The tailing '='s are optional, but if they're present, should be removed 

預期的結果：

h1. This is the first line 
h1. This is the first line again 
h2. This is the second line 
h3. This is the third line 
h4. This is the forth line 
h4. The tailing '='s are optional, but if they're present, should be removed 

任何語言好吧（python，perl，bash更好）。

Answer 1

通過Python。

import re 
with open('input.txt', 'r') as f:         # Open the text file for reading 
    for line in f:             # iterate through all the lines 
     if line.startswith('='):         # Do the below operation only on the lines which starts with `=` symbol. 
      finalcount = line.split()[0].count('=')     # Count the number of `=` symbols located on the first word only. 
      line = re.sub(r'=+$', r'', line)      # Remove all the trailing `=` symbols if it's presented. 
      line = re.sub(r'^\S+', r'h'+str(finalcount)+'.', line) # Replace the first word in the lines which startswith `=` with `h` plus the value stores in finalcount variable plus a dot. 
      print(line, end='')          # Now print the modified line. 

輸出：

h1. This is the first line 
h1. This is the first line again 
h2. This is the second line 
h3. This is the third line 
h4. This is the forth line 
h4. The tailing '='s are optional, but if they're present, should be removed