Read string up to a certain size in Python

Question

I have a string stored in a variable. Is there a way to read a string up to a certain size e.g. File objects have f.read(size) which can read up to a certain size?

Slice notation won't overrun a string: `s = 'f' * 5; t = s[:50]` — anthony sottile, Feb 05 '16 at 16:23
Yes I want something like substring but using the given size in bytes — Boeingfan, Feb 05 '16 at 16:25
Are you sure you want bytes and not characters? (Don't forget unicode) — ThinkChaos, Feb 05 '16 at 16:31
Basically I want send a string over a socket so I need to split my string in chunks — Boeingfan, Feb 05 '16 at 16:37

score 0 · Answer 1 · edited May 23 '17 at 12:07

Check out this post for finding object sizes in python.

If you are wanting to read the string from the start until a certain size MAX is reached, then return that new (possibly shorter string) you might want to try something like this:

import sys

MAX = 176 #bytes
totalSize = 0
newString = ""

s = "MyStringLength"

for c in s:
    totalSize = totalSize + sys.getsizeof(c)
    if totalSize <= MAX:
        newString = newString + str(c)
    elif totalSize > MAX:
        #string that is slightly larger or the same size as MAX
        print newString
        break

This prints 'MyString' which is less than (or equal to) 176 Bytes.

Hope this helps.

Just saw you want 'size' in characters and not bytes. John's post then seems more appropriate. — Benjamin Castor, Feb 05 '16 at 19:38

score 0 · Answer 2 · answered Feb 05 '16 at 16:56

message = 'a long string which contains a lot of valuable information.'
bite = 10

while message:
    # bite off a chunk of the string
    chunk = message[:bite]

    # set message to be the remaining portion
    message = message[bite:]

    do_something_with(chunk)

Read string up to a certain size in Python

2 Answers2