string length without len function in python

Question

hi can anyone tell me how can i get the length of a string if a user input it and we want to know the length of the string without sing len function or any string methods please anyone tell me as i m tapping me head madly for the answer..... thank you

Answer 1

Why you need to avoid the len function is beyond me, but strings are iterables. You should be able to do this:

strlen = 0

for c in myString:
  strlen += 1

Answer 2

easy:

length=0
for x in "This is a string":
    length+=1
print(length)

Answer 3

>>> sum(map(lambda x:1, "hello world"))
11

>>> sum(1 for x in "foobar")
6

>>> from itertools import count
>>> zip(count(1), "baz")[-1][0]
3

some recursive solutions

>>> def get_string_length(s):
...     return 1 + get_string_length(s[1:]) if s else 0
... 
>>> get_string_length("hello world")
11
>>> def get_string_length_gen(s):
...     yield 1 + next(get_string_length_gen(s[1:])) if s else 0
... 
>>> next(get_string_length_gen("hello world"))
11
>>> 

Answer 4

It's a weird question so here's a weird answer!

try:
  for i in itertools.count(): mystring[i]
except IndexError:
  pass

Answer 5

>>> import re
>>> s
'mylongstring'
>>> re.subn(".","1",s)[-1]
12
>>>

If string contains new lines

>>> s="mys\ntring\n"
>>> re.compile(".",re.DOTALL).subn("",s)[-1]
10

Answer 6

Not very efficient but very concise:

def string_length(s):    
    if s == '': return 0
    return 1 + string_length(s[1:])

Answer 7

Here's an O(1) method:

def strlen(s):
    if s == "": return 0
    return s.rindex(s[-1]) + 1

In other words, it doesn't work by counting the characters, so should be just as fast for a 1GB string as it is for a 1 byte string.

It works by looking at the last character and searching from the very end to find that character. Since it's the last character it will always find it at the first place it looks, essentially always returning the index of the last character. The length is just one more than the index of the last character.

Answer 8

Here's a way to do it by counting the number of occurences of the empty string within the string:

def strlen(s):
    return s.count('') - 1

Since "".count("") returns 1, you have to subtract 1 to get the string's length.

Answer 9

Make a file-like object from the string, read the entire object, then tell your offset:

>>> import StringIO
>>> ss = StringIO.StringIO("ABCDEFGHIJ")
>>> ss.read()
'ABCDEFGHIJ'
>>> ss.tell()
10