reverse a string in Python
How to reverse a string?
Simple! :-)
s = 'abc'
s = s[::-1]
print s
Simple! :-)
lambda magic to find prime numbers
Find prime number up to 100 with just 3 lines of code. The 4th line is for printing ;) nums = range(2, 100) for i in range(2, 10): nums = filter(lambda x: x == i or x % i, nums) print nums Isn't it amazing? Check my new post about Prime number: http://love-python.blogspot.com/2010/11/prime-number-generator-in-python-using.html
Comments
--Hans
it really helpful.
thanks.
or any link for explanation will be helpful.
thanks.
Example:
>>> foo = [2, 5, 1, 8]
Regular slice (returns all)
>>> foo[:]
[2, 5, 1, 8]
Slice with stride (returns every nth)
>>> foo[::2]
[2, 1]
Stride works inversely as well
>>> foo[::-2]
[8, 5]
Hence it can be used to reverse a string (stride backwards using step length of one)
>>> 'foobar'[::-1]
'raboof'
There is another way to reverse as well. This can be done using "reversed" generator:
>>> ''.join([char for char in reversed('foobar')])
'raboof'
As the list comprehension returns a list I had to join it separately. Normally the [::-1] trick should work just fine. "reversed" may be useful in some special cases, however.
Check out http://www.python.org/doc/2.3.5/whatsnew/section-slices.html for more comprehensive documentation.
s = s[::2]
print s
#for this code it returns ac
#how
Does anyone know what i should use to extract string/substring from a string?
print $string = reverse("ABC")
>>>print s[:]
spam
>>>print s[::-1]
maps
>>>print s[0:len(s)]
spam
>>>print s[0:len(s):-1]
(prints nothing)
Any reason, why ??
s='abc'
print s[::-2]
returns 'ca' only...
You could do this:
oct(12)
that would return
'014' as a string
To enter an octal number literal, precede with a 0:
0122 will return 82 in base 10
to go from an octal string to an int:
int('014',8)
>>> sentence = "one two three four"
>>> ' '.join( [ word[::-1] for word in sentence.split() ] )[::-1]
'four three two one'
>>> sentence = "one two three four"
>>> ' '.join( [ word for word in sentence.split() ] [::-1])
'four three two one'
[::-1]
[:] <-- this gets all of the string
while [::(value)] skips or reverse the string. if it is negative, the skipping starts from the last character of the string depends on the number.
for example, you can put -2 instead of -1.
s = 'abcdef'
s = s[::-2]
print s
if counted base on the slice number, it would creat a group of three which are fe, dc and ba. the first character of each group (f,d,b) will appended to formed a value and stored it to the variable 's'.
revword = ''
for letter in reversed(word): revword += letter
print revword
Full code solutions with test data and output, described in clear English and tested on the same page
print (" ".join(str.split()[::-1])) would work for reversing string word by word :)
Thought to share it . :)