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
