Operations with strings in python

Question

Currently I'm learning Python3, and I already have some experience with C. I need to shift string to get rid of two first bytes. Here's code in C:

char *a = "Hello World";
a += 2;
printf ("%s", a)

this program will output "llo World"

I was wondering if there is a way of doing such thing in Python efficiently, without copying the whole string.

• Aaron D: Python isn't used to be efficient in the way you mean. The language has its own paradigm of 'Pythonic' code conventions, and using pointers to address memory spaces directly is not common. The answers to this question are all the standard "Pythonic" way to do things - treat the string as a list of characters and return a new list with the substring you want.

Answer 1

The closest operation in 2.x would be creating a buffer from the string and then slicing that. Creating the buffer is an additional operation, but only needs to be performed once since the buffer can be reused.

>>> a = 'Hello world'
>>> b = buffer(a)
>>> print b[2:]
llo world
>>> print b[:5]
Hello

3.x doesn't have buffer, but you shouldn't be trying to emulate the C code in Python regardless. Figure out what you're actually trying to do, and then write the appropriate Pythonic code for it.

• interjay: Does Python 3 have buffer? I know it has memoryview, but I don't think that works on str objects.
• Ignacio Vazquez-Abrams: No, buffer is gone in 3.x. But you shouldn't be trying to emulate C in Python regardless, unless you want to write slower code.
• interjay: OP did say he was using Python 3 though.

Answer 2

Python is higher level than C and understands what a string is. You can do:

s = "Hello World"
print(s[2:])

You can find more here: https://docs.python.org/3/tutorial/introduction.html#strings.

• Ignacio Vazquez-Abrams: Slicing a string copies the elements.
• qsantos: Well, you can use a memoryview but it's probably not worth it in most cases and definitely not for a beginner.

Answer 3

Sure there is and is better than C

a = "Hello World"
print a[2:]

This is called slicing

Refer the image

enter image description here

• markcial: and the third parameter for the increment in the slicing, meaning that with [::-1] you will get the list reversed
• interjay: This does copy the sliced elements, unlike the C code.
• markcial: i will remember that then, ok

Answer 4

FYI : You don't need to declare any variable, you can do the operations on the string directly

"Hello world"[2:] # llo world