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Python len[] function returns the length of the string.
Python len[] Syntax
Syntax: len[string]
Return: It returns an integer which is the length of the string.
Python len[] Example
len[] methods with string in Python.
Python3
string
=
"Geeksforgeeks"
print
[
len
[string]]
Output:
13
Example 1: Len[] function with tuples and string
Here we are counting length of the tuples and list.
Python
tup
=
[
1
,
2
,
3
]
print
[
len
[tup]]
l
=
[
1
,
2
,
3
,
4
]
print
[
len
[l]]
Output:
3 4
Example 2: Python len[] TypeError
Python3
Output:
TypeError: object of type 'bool' has no len[]
Example 3: Python len[] with dictionaries and sets
Python3
dic
=
{
'a'
:
1
,
'b'
:
2
}
print
[
len
[dic]]
s
=
{
1
,
2
,
3
,
4
}
print
[
len
[s]]
Output:
2 4
Example 4: Python len[] with custom objects
Python3
class
Public:
def
__init__[
self
, number]:
self
.number
=
number
def
__len__[
self
]:
return
self
.number
obj
=
Public[
12
]
print
[
len
[obj]]
Output:
12
Time complexity :
len[] function has time complexity of O[1]. in average and amortized case
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Strings in Python are immutable sequences of Unicode code points. Given a string, we need to find its length. Examples:
Input : 'abc' Output : 3 Input : 'hello world !' Output : 13 Input : ' h e l l o ' Output :14
Methods#1:
- Using the built-in function len. The built-in function len returns the number of items in a container.
Python3
str
=
"geeks"
print
[
len
[
str
]]
Method#2:
- Using for loop and in operator. A string can be iterated over, directly in a for loop. Maintaining a count of the number of iterations will result in the length of the string.
Python3
def
findLen[
str
]:
counter
=
0
for
i
in
str
:
counter
+
=
1
return
counter
str
=
"geeks"
print
[findLen[
str
]]
Method#3:
- Using while loop and Slicing. We slice a string making it shorter by 1 at each iteration will eventually result in an empty string. This is when while loop stops. Maintaining a count of the number of iterations will result in the length of the string.
Python3
def
findLen[
str
]:
counter
=
0
while
str
[counter:]:
counter
+
=
1
return
counter
str
=
"geeks"
print
[findLen[
str
]]
Method#4:
- Using string methods join and count. The join method of strings takes in an iterable and returns a string which is the concatenation of the strings in the iterable. The separator between the elements is the original string on which the method is called. Using join and counting the joined string in the original string will also result in the length of the string.
Python3
def
findLen[
str
]:
if
not
str
:
return
0
else
:
some_random_str
=
'py'
return
[[some_random_str].join[
str
]].count[some_random_str]
+
1
str
=
"geeks"
print
[findLen[
str
]]
Method:5:
- Using reduce method. Reduce method is used to iterate over the string and return a result of collection element provided to the reduce function. We will iterate over the string character by character and count 1 to result each time.
Python3
import
functools
def
findLen[string]:
return
functools.
reduce
[
lambda
x,y: x
+
1
, string,
0
]
string
=
'geeks'
print
[findLen[string]]
Output:
5
Method:6:
- Using sum[] and list comprehension function. We use list comprehension for iterating over the string and sum function to sum total characters in string
Python3
def
findLen[string]:
return
sum
[
1
for
i
in
string];
string
=
'geeks'
print
[findLen[string]]
Output:
5