What is a Python String and String Function in Python?
Python string is an ordered collection of characters which is used to represent and store the text-based information. Strings are stored as individual characters in a contiguous memory location. It can be accessed from both directions: forward and backward. Characters are nothing but symbols. Strings are immutable Data Types in Python, which means that once a string is created, they cannot be changed. In this module, we will learn all about strings in Python so as to get started with strings.
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Following is the list of all topics that are covered in this module.
- Creating a String in python
- Accessing Python String Characters
- Updating or Deleting a String in Python
- Python String Operators
- Built-in Python String Methods and Python String Functions
So, without any further ado, let’s get started.
Creating a String in Python
In Python, strings are created using either single quotes or double quotes. We can also use triple quotes, but usually triple quotes are used to create docstrings or multi-line strings.
#creating a string with single quotes String1 = ‘Intellipaat’ print (String1)#creating a string with double quotes String2 = “Python tutorial” Print (Strings2)
After creating strings, they can be displayed on the screen using the print () method as shown in the above example. The output of the above example will be as follows:
Intellipaat Python Tutorial
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Accessing Python String Characters
In Python, the characters of string can be individually accessed using a method called indexing. Characters can be accessed from both directions: forward and backward. Forward indexing starts form 0, 1, 2…. Whereas, backward indexing starts form −1, −2, −3…, where −1 is the last element in a string, −2 is the second last, and so on. We can only use the integer number type for indexing; otherwise, the TypeError will be raised.
String1 = ‘intellipaat’ print (String1) print (String1) print (String1) print (String1[-1]) Output: Intellipaat i n t
Updating or Deleting a String in Python
As discussed above, strings in Python are immutable and thus updating or deleting an individual character in a string is not allowed, which means that changing a particular character in a string is not supported in Python. Although, the whole string can be updated and deleted. The whole string is deleted using a built-in ‘del’ keyword.
#Python code to update an entire string String1 = ‘Intellipaat Python Tutorial’ print (“original string: “) print (String1)String1 = ‘Welcome to Intellipaat’ print (“Updated String: “) print (String1) Output: Original String: Intellipaat Python Tutorial Updated String: Welcome to Intellipaat
#Python code to delete an entire string String1 = ‘Intellipaat Python tutorial’ print (String1) del String1 print (String1) Output: Intellipaat Python tutorial Traceback (most recent call last): File “”, line 1, in NameError: name ‘String1’ is not defined
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Python Operators for Strings
There are three types of operators supported by a string, which are:
- Basic Operators (+, *)
- Relational Operators (<, ><=, >=, ==, !=)
- Membership Operators (in, not in)
Table: Common String Constants and Operations
|s1 = ‘ ’||Empty string|
|s2 = “a string”||Double quotes|
|block = ‘‘‘…’’’||Triple-quoted blocks|
|s1 + s2||Concatenate|
|s2 * 3||Repeat|
|“a %s parrot” % ‘dead’||String formatting in Python|
|for x in s2||Iteration|
|‘m’ in s2||Membership|
Table: String Backslash Characters
|\newline||Ignored (a continuation)|
|\n||Newline (ASCII line feed)|
|\\||Backslash (keeps one \)|
|\’||Single quote (keeps ‘)|
|\”||Double quote (keeps “)|
|\0XX||Octal value XX|
|\xXX||Hex value XX|
|\000||Null (doesn’t end string)|
Example: Program to concatenate two strings.
S1 = “hello” S2 = “Intellipaat” print (S1 + S2)
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Built-in Python String Methods and Python String Functions
Let’s understand all the standard built-in methods/ string function in Python through the following table:
|String Method/String Function in Python||Description of String Method/String Function in Python|
|capitalize()||It capitalizes the first letter of a string.|
|center(width, fillchar)||It returns a space-padded string with the original string centered to.|
|count(str, beg= 0,end=len(string))||It counts how many times ‘str’ occurs in a string or in the substring of a string if the starting index ‘beg’ and the ending index ‘end’ are given.|
|encode(encoding=’UTF-8′,errors=’strict’)||It returns an encoded string version of a string; on error, the default is to raise a ValueError unless errors are given with ‘ignore’ or ‘replace’.|
|endswith(suffix, beg=0, end=len(string))||It determines if a string or the substring of a string (if the starting index ‘beg’ and the ending index ‘end’ are given) ends with a suffix; it returns true if so, and false otherwise.|
|expandtabs(tabsize=8)||It expands tabs in a string to multiple spaces; defaults to 8 spaces per tab if the tab size is not provided.|
|find(str, beg=0 end=len(string))||It determines if ‘str’ occurs in a string or in the substring of a string if starting index ‘beg’ and ending index ‘end’ are given and returns the index if found, and −1 otherwise.|
|index(str, beg=0, end=len(string))||It works just like find() but raises an exception if ‘str’ not found.|
|isalnum()||It returns true if a string has at least one character and all characters are alphanumeric, and false otherwise.|
|isalpha()||It returns true if a string has at least one character and all characters are alphabetic, and false otherwise.|
|isdigit()||It returns true if a string contains only digits, and false otherwise.|
|islower()||It returns true if a string has at least one cased character and all other characters are in lowercase, and false otherwise.|
|isupper()||It returns true if a string has at least one cased character, and all other characters are in uppercase, and false otherwise.|
|len(string)||It returns the length of a string.|
|max(str)||It returns the max alphabetical character from the string str.|
|min(str)||It returns the min alphabetical character from the string str.|
|upper()||It converts lowercase letters in a string to uppercase.|
|rstrip()||It removes all trailing whitespace of a string.|
|split(str=””, num=string.count(str))||It is used to split strings in Python according to the delimiter str (space if not provided any) and returns the list of substrings in Python|
|splitlines( num=string.count(‘\n’))||It splits a string at the newlines and returns a list of each line with newlines removed.|
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This brings us to the end of this module in Python Tutorial. Now, if you are interested in knowing why Python is the most preferred language for data science, you can go through this Python for Data Science blog..
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