What is String in Python?
A string is a sequence of characters, where each character has a unique position/index. The index of the string starts from 0 to length-1 in the forward direction and -1,-2,-3 …. Length-1 in the backward direction.
A character is simply a symbol. For example, the English language has 26 characters.
In real computer do not deal with characters, they deal with numbers (binary numbers). Even though you may see characters on your screen, internally it is stored and manipulated as a combination of 0’s and 1’s.
This conversion of character to a number is called encoding, and the reverse process is decoding. ASCII and Unicode are some of the popular encoding used.
In Python, the string is a sequence of Unicode characters. Unicode was introduced to include every character in all languages and bring uniformity in encoding.
How to create a string in Python?
Strings can be created by enclosing characters inside a single quote or double-quotes. Even triple quotes can be used in Python but generally used to represent multiline strings and docstrings.
# all of the following are equivalent
n = ‘Hello how are you’
print(n)
n = “Hello how are you”
print(n)
n = ”’Hello how are you”’
print(n)
# triple quotes string can extend to multiple lines
n = “””Hello, how are you
welcome to Python strings “””
print(n)
Output:
Example:
n = 'Hello how are you'
print(n)
n = "Hello how are you"
print(n)
n = '''Hello how are you'''
print(n)
# triple quotes string can extend to multiple lines
n = """Hello, how are you
welcome to Python strings """
print(n)
Output:
Hello how are you
Hello how are you
Hello how are you
Hello, how are you
welcome to Python strings
>>>
How to access characters in a string?
We can access individual characters using indexing and a range of characters using slicing. The index starts from 0. Trying to access a character out of index range will raise an IndexError.
The index must be an integer. We can’t use float or other types, this will result in TypeError.
Python allows negative indexing for its sequences. The index of -1 refers to the last item, -2 to the second last item, and so on. We can access a range of items in a string by using the slicing operator (colon).
Positive index
Example:1
n=”computer”
Positive index
|
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
c |
o |
m |
p |
u |
t |
e |
r |
n=”computer”
print(n)
print(n[0])
print(n[2])
print(n[4])
print(n[5])
print(n[7])
output:
computer
c
m
u
t
r
n="computer" print(n) print(n[0]) print(n[2]) print(n[4]) print(n[5]) print(n[7])
Output:
computer c m u t r >>>
Example:2
n1=”catalyst”
Positive index
|
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
c |
a |
t |
a |
l |
y |
s |
t |
n1=’catalyst’
print(n1)
print(n1[0])
print(n1[2])
print(n1[4])
print(n1[5])
print(n1[7])
output:
catalyst
c
t
l
y
t
n1='catalyst' print(n1) print(n1[0]) print(n1[2]) print(n1[4]) print(n1[5]) print(n1[7])
Output:
catalyst c t l y t >>>
Negative indexing
Example:3
n=”computer”
Positive index
|
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
c |
O |
m |
p |
u |
t |
e |
r |
|
-8 |
-7 |
-6 |
-5 |
-4 |
-3 |
-2 |
-1 |
Negative index
n=”computer”
print(n)
print(n[-0])
print(n[-2])
print(n[-4])
print(n[-5])
print(n[-7])
output:
computer
c
e
u
p
o
n="computer" print(n) print(n[-0]) print(n[-2]) print(n[-4]) print(n[-5]) print(n[-7])
Output:
computer c e u p o >>>
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