>>> 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
A "tongue twister"
>>> sum(not out not in out for out in "shake it all about")
18
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
>>>
>>> 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
A "tongue twister"
>>> sum(not out not in out for out in "shake it all about")
18
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
>>>
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.
You probably need to initialize your variable j (here under renamed counter):
def string_length(my_string):
"""returns the length of a string
"""
counter = 0
for char in my_string:
counter += 1
return counter
# taking user input
string_input = input("enter string :")
length = string_length(string_input)
print("length is ", length)
This could also be done in one "pythonic" line using a generator expression, as zondo has pointed out:
def string_length(my_string):
"""returns the length of a string
"""
return sum(1 for _ in my_string)
It's quite simple:
def string_length(string):
return sum(1 for char in string)
1 for char in string is a generator expression that generates a 1 for each character in the string. We pass that generator to sum() which adds them all up. The problem with what you had is that you didn't define j before you added to it. You would need to put j = 0 before the loop. There's another way that isn't as nice as what I put above:
from functools import reduce # reduce() is built-in in Python 2.
def string_length(string):
return reduce(lambda x,y: x+1, string, 0)
It works because reduce() calls the lambda function first with the initial argument, 0, and the first character in the string. The lambda function returns its first argument, 0, plus one. reduce() then calls the function again with the result, 1, and the next character in the string. It continues like this until it has passed every character in the string. The result: the length of the string.
Hi I need help I don’t know how to input validate the length of a string so In pseudocode I wanna do this
Input a 3 character name
Check if name is 3 characters
if not then print error so if it’s anything but 3 letters long I wanna say you can’t do that do it again
I know how to do input validation algorithm for integers etc I learned that in school but this assignment is telling me to do something I didn’t learn lol I’ve tried on the internet and it don’t give me an answer
Kind of odd but is there a way to find a length of an integer without using len(str(int)) ? Or without type casting?