On 01/19/2014 02:59 PM, rahmad akbar wrote:> hey guys, super noob here, i am
trying to understand the following code
from google tutorial which i failed to comprehend
#code start
# E. not_bad
# Given a string, find the first appearance of the
# substring 'not' and 'bad'. If the 'bad' follows
# the 'not', replace the whole 'not'...'bad' substring
# with 'good'.
# Return the resulting string.
# So 'This dinner is not that bad!' yields:
# This dinner is good!
def not_bad(s):
# +++your code here+++
# LAB(begin solution)
n = s.find('not')
b = s.find('bad')
if n != -1 and b != -1 and b > n:
s = s[:n] + 'good' + s[b+3:]
return s
#code end
on the following lines, what is -1, is that index number? and i dont
understand the entire second line
-1 is what find returns if the searched substring is not at all present in the
bigger string: a trick meaning "could not find it". (-1 also means last index,
but is not necessary for find, it would return the positive last index)
if n != -1 and b != -1 and b > n:
a conditions for which 3 sub-conditions must be met at once
s = s[:n] + 'good' + s[b+3:]
Watch this:
string: This dinner is not that bad!
indexes: 0 n b -1
s[:n] = s[0:n] = "This dinner is "
s[b+3:] = s[b+3:-1] = "!"
+ concatenates (glues together) bits of strings
denis
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