给字符串填充0

有什么方法可以给字符串左边填充0,这样就可以有一个特定长度.

字符串:

>>> n = '4'
>>> print n.zfill(3)
>>> '004'

对于数字:

>>> n = 4
>>> print '%03d' % n
>>> 004
>>> print format(4, '03') # python >= 2.6
>>> 004
>>> print "{0:03d}".format(4)  # python >= 2.6
>>> 004
>>> print("{0:03d}".format(4))  # python 3
>>> 004

>>> t = 'test'
>>> t.rjust(10, '0')
>>> '000000test'