Till now, we have discussed numbers as the standard data types in python. In this section of the tutorial, we will discuss the most popular data type in python i.e., string.
In python, strings can be created by enclosing the character or the sequence of characters in the quotes. Python allows us to use single quotes, double quotes, or triple quotes to create the string.
Consider the following example in python to create a string.
str = "Hi Python !"
Here, if we check the type of the variable str using a python script
print(type(str)), then it will print string (str).
In python, strings are treated as the sequence of strings which means that python doesn't support the character data type instead a single character written as 'p' is treated as the string of length 1.
Strings indexing and splitting
Like other languages, the indexing of the python strings starts from 0. For example, The string "HELLO" is indexed as given in the below figure.
Python String
As shown in python, the slice operator [] is used to access the individual characters of the string. However, we can use the : (colon) operator in python to access the substring. Consider the following example.
Python String
Here, we must notice that the upper range given in the slice operator is always exclusive i.e., if str = 'python' is given, then str[1:3] will always include str[1] = 'p', str[2] = 'y', str[3] = 't' and nothing else.
Reassigning strings
Updating the content of the strings is as easy as assigning it to a new string. The string object doesn't support item assignment i.e., A string can only be replaced with a new string since its content can not be partially replaced. Strings are immutable in python.
Consider the following example.
Example 1
str = "HELLO"
str[0] = "h"
print(str)
Output:
Traceback (most recent call last):
File "12.py", line 2, in <module>
str[0] = "h";
TypeError: 'str' object does not support item assignment
However, in example 1, the string str can be completely assigned to a new content as specified in the following example.
Example 2
str = "HELLO"
print(str)
str = "hello"
print(str)
Output:
HELLO
hello
String Operators
Operator
Description
+
It is known as concatenation operator used to join the strings given either side of the operator.
*
It is known as repetition operator. It concatenates the multiple copies of the same string.
[]
It is known as slice operator. It is used to access the sub-strings of a particular string.
[:]
It is known as range slice operator. It is used to access the characters from the specified range.
in
It is known as membership operator. It returns if a particular sub-string is present in the specified string.
not in
It is also a membership operator and does the exact reverse of in. It returns true if a particular substring is not present in the specified string.
r/R
It is used to specify the raw string. Raw strings are used in the cases where we need to print the actual meaning of escape characters such as "C://python". To define any string as a raw string, the character r or R is followed by the string.
%
It is used to perform string formatting. It makes use of the format specifiers used in C programming like %d or %f to map their values in python. We will discuss how formatting is done in python.
Example
Consider the following example to understand the real use of Python operators.
str = "Hello"
str1 = " world"
print(str*3) # prints HelloHelloHello
print(str+str1)# prints Hello world
print(str[4]) # prints o
print(str[2:4]); # prints ll
print('w'in str) # prints false as w is not present in str
print('wo'notin str1) # prints false as wo is present in str1.
print(r'C://python37') # prints C://python37 as it is written
print("The string str : %s"%(str)) # prints The string str : Hello
Output:
HelloHelloHello
Hello world
o
ll
False
False
C://python37
The string str : Hello
Python Formatting operator
Python allows us to use the format specifiers used in C's printf statement. The format specifiers in python are treated in the same way as they are treated in C. However, Python provides an additional operator % which is used as an interface between the format specifiers and their values. In other words, we can say that it binds the format specifiers to the values.
Consider the following example.
Integer = 10;
Float = 1.290
String = "Ayush"
print("Hi I am Integer ... My value is %d\nHi I am float ... My value is %f\nHi I am string ... My value is %s"%(Integer,Float,String));
Output:
Hi I am Integer ... My value is 10
Hi I am float ... My value is 1.290000
Hi I am string ... My value is Ayush
Built-in String functions
Python provides various in-built functions that are used for string handling. Many String fun
It returns true if the characters in the string are alphanumeric i.e., alphabets or numbers and there is at least 1 character. Otherwise, it returns false.
It returns true if the string is titled properly and false otherwise. A title string is the one in which the first character is upper-case whereas the other characters are lower-case.
It searches for the separator sep in S, and returns the part before it, the separator itself, and the part after it. If the separator is not found, return S and two empty strings.
maketrans()
It returns a translation table to be used in translate function.
It is same as split() but it processes the string from the backward direction. It returns the list of words in the string. If Separator is not specified then the string splits according to the white-space.
Splits the string according to the delimiter str. The string splits according to the space if the delimiter is not provided. It returns the list of substring concatenated with the delimiter.
