Strings in python
Many of us who are familiar with programming languages like C, C++ etc. will have an answer like “String is a collection or array of characters.”
Well in Python also, we say the same definition for String data type. String is array of sequenced characters and is written inside single quotes, double quotes or triple quotes. Also, Python doesn’t have character data type, so when we write ‘a’, it is taken as a string with length 1.
Moving on with this article on what is String in Python?
How to create a string?s = 'Hello'
print(s)
s1 = "Hello"
print(s1)
s2 = ''' Hello
How is the whether today? '''
print(s2)
Output:
Hello
Hello
Hello
How is the whether today?
Triple quotes are used usually when we have both single and double quotes in the string and also when we want to write multi-line sentences.
Note
We need to take care that while using single quotes, the string should not include single quote in it because if that happens, Python will assume that the line is finished with the occurrence of the second quote itself and desired output will not be fetched. Same notation should be followed with double quotes and triple quotes also.
Moving on with this article on what is String in Python?
How to access a character from a string?
Suppose we want to access a character from a string, let’s say the last character, we need to know it’s position in the string.
Here is a string along with the position allocated. So if we want to access ’n’ from the string, we have to go to the 5th position to have it.
The numbering or indexing starts from 0 to one less than the length of string.
Here is a python program to make us more clear in that.
str = 'Antarctica is really cold.'
print('str = ', str)
#first character
print('str[0] = ', str[0])
#last character
print('str[-1] = ', str[-1])
#slicing 2nd to 5th character
print('str[1:5] = ', str[1:5])
#slicing 6th to 2nd last character
print('str[5:-2] = ', str[5:-2])
Output:
str = Antarctica is really cold.
str[0] = A
str[-1] = .
str[1:5] = ntar
str[5:-2] = ctica is really col
Now if left to right follows increasing order pattern in indexing, right to left follows decreasing order pattern i.e. from -1, -2, -3 so on. So if you want to access the last character, you can do it in two ways.
str = 'Antarctica is really cold.'
a = len(str)
print('length of str ', a)
#last character with the help of length of the string
print('str[a] ', str[a-1])
#last character with the help of indexing
print('str[-1] ',str[-1])
Output:
length of str 26
str[a] .
str[-1] .
Strings are immutable in nature which implies that once a string has been declared, any character in it cannot be changed.
s = "Hello Batman"
print(s)
s[2] = 'P'
print(s)
Output:
Hello Batman
Traceback (most recent call last):
File “C:/Users/prac.py”, line 3, in
s[2] = ‘P’
TypeError: ‘str’ object does not support item assignment
Process finished with exit code 1
However you can delete the whole string with del operator.
s = "Hello Batman"
print(s)
del s
print(s)
Output:
Hello Batman
Traceback (most recent call last):
File “C:/Users/prac.py”, line 4, in
print(s)
NameError: name ‘s’ is not defined
If you don’t want s to be “Hello Batman” and want it to be some other string, then you can just update the string as a whole.
s = "Hello Batman"
print(s)
s = "Hello Spiderman"
print(s)
Output:
Hello Batman
Hello Spiderman
Formatting a String:
Formatting a string means to allocate the string dynamically wherever you want.
Strings in Python can be formatted with the use of format() method which is very versatile and powerful tool for formatting of Strings. Format method in String contains curly braces {} as placeholders which can hold arguments according to position or keyword to specify the order.
String1 = "{} {} {}".format('Hello', 'to', 'Batman')
print("Default order: ")
print(String1)
# Positional Formatting
String1 = "{1} {0} {2}".format('Hello', 'to', 'Batman')
print("nPositional order: ")
print(String1)
# Keyword Formatting
String1 = "{c} {b} {a}".format(a='Hello', b='to', c='Spiderman')
print("nString in order of Keywords: ")
print(String1)
# Formatting of Integers
String1 = "{0:b}".format(20)
print("binary representation of 20 is ")
print(String1)
# Formatting of Floats
String1 = "{0:e}".format(188.996)
print("nExponent representation of 188.996 is ")
print(String1)
# Rounding off Integers
String1 = "{0:.2f}".format(1 / 6)
print("none-sixth is : ")
print(String1)
# String alignment
String1 = "|{:<10}|{:^10}|{:>10}|".format('Hello', 'to', 'Tyra')
print("nLeft, centre and right alignment with Formatting: ")
print(String1)
Output:
Default order:
Hello to Batman
Positional order:
to Hello Batman
String in order of Keywords:
Spiderman to Hello
Binary representation of 20 is 10100
Exponent representation of 188.996 is
1.889960e+02
one-sixth is :
0.17
Left, center and right alignment with Formatting:
|Hello | to | Tyra|A string can be left (<), right(>) or center (^) justified with format method.
{:<10}.format(“Hello”) means Python will reserve 10 space for the string and the string will start from the left. The same goes with right and center justification