format string?
conversion characters:
r ? ? raw string
s ? ? string
% ? a '%' character
f ? ? floating point number
e ? ?floating point number exponential format ( lowercase )
i ? ? signed integer
print 'i like %s like %s%s' % ('nothing','this'+'ever','hi')
## string+string is considered as one string
round(number[,ndigits]) ?(四舍五入）
Return the floating point value?number?rounded to?ndigits?digits after the decimal point. If?ndigits?is omitted, it defaults to zero. The result is a floating point number. Values are rounded to the closest multiple of 10 to the power minus?ndigits; if two multiples are equally close, rounding is done away from 0 (so, for example, round(0.5) is 1.0 and round(-0.5)is-1.0).
Note
The behavior of?round()?for floats can be surprising: for example, round(2.675,2)gives2.67instead of the expected2.68. This is not a bug: it’s a result of the fact that most decimal fractions can’t be represented exactly as a float. ?SeeFloating Point Arithmetic: Issues and Limitations?for more information.
slicing
>>> 'abcd'[0:2]
'ab' ? ? ? ? ? ? ? ?## left : close ?right : open
>>> 'hello' == 'HELLO'
False ? ? ? ? ? ?## uppercase and lowercase are different
>>> 'world'[:-1]
'worl' ? ? ? ? ? ? ## if not pointed out, from left to right
