虽然可以用CSS，但还是想用Python实现

初步想法：
python分析出标题级别，加上数字标号

str="""#       
##       
###      
###   
##
#
##
### 
#### 
####    
#
##
#######
###"""




lines = str.split("\n")
stepUp = 0
titleNum = [0,0,0,0,0,0,0,0,0,0,0,0,0]
lastLevel = 0
for line in lines:
    c= line.count('#')
#     print(c,lastLevel,stepUp,titleNum,line)
  
    
    if lastLevel>c:
        stepUp = c
        titleNum[stepUp]+=1
        for i in range(c+1,6):
            titleNum[i] = 0
    else:
        titleNum[c]+=1
    lastLevel = c
    print(c,lastLevel,stepUp,titleNum,line)
#     print("============")

结果