Python recipe(5):Indentation

代码先行：

Example Source Code [http://www.cnblogs.com/tomsheep/]

'''
Created on 2010-5-21

@author: lk
'''
#trip and add spaces
def reindent(s, numofSpaces):
    s = s.split('\n')
    s = [numofSpaces * ' ' + line.lstrip() for line in s]
    s = '\n'.join(s)
    return s

#do not trip
def addSpaces(s, numAdd):
    white = ' ' * numAdd
    return white + white.join(s.splitlines(1))

def delSpaces(s, numDel):
    def aux(line, numDel=numDel, white=' ' * numDel):
        if line[:numDel] != white:
            raise ValueError, 'removing more spaces than there are!'
        return line[numDel:]
    return ''.join(map(aux, s.splitlines(1)))

def numOfSpaces(s):
    return [len(line)-len(line.lstrip()) for line in s.splitlines(1)]

def unIndentBlock(s):
    return delSpaces(s, min(numOfSpaces(s)))

if __name__ == '__main__':
    s = ' ' * 5 + "Hello \n" + ' ' * 7 + "World"
    print reindent(s, 5)
    print reindent(s, 10)
    
    print addSpaces(s, 2)
    print delSpaces(s, 2)

    print numOfSpaces(s)
    print unIndentBlock(s)

以上代码改写自Python Cookbook 3-12

概述：

    对多行字符块进行缩进。其中reindent函数首先左对齐（删除空白），然后添加相应数量空白符；addSpaces不删除每行开头原有的空白符；delSpaces函数去除每行相应数目的空白符；numOfSpaces计算每行开头的空白符数

代码说明：

1. string对象的splitlines函数，依照换行符分割字符串，若参数为True则保留换行符，默认False。和string对象的split(‘\n’)等价