001_015 Python拡張タブと圧縮タブは、タブを一定数のスペースに置き換えるか、逆に置き換える

#encoding=utf-8
print '  '

#        

str='1\t2
 \t '
ustr=u' \t '
print str.expandtabs()
print ustr.expandtabs(4)

#                     
import re #               tab    'a'  '\t','b'   ' '，         
def unexpand(astring, tablen=8):
    pieces = re.split(r'( +)',astring.expandtabs())
    lensofar=0 #     
    for i ,piece in enumerate(pieces):
        thislen=len(piece)
        lensofar += thislen
        if piece.isspace():
            numblanks = lensofar % tablen
            numtabs = (thislen - numblanks + tablen -1)/tablen
            pieces[i] ='a'*numtabs+'b'*numblanks
    return ''.join(pieces)

str='1        2        3'
print unexpand(str)