Introduction to Strings in Python

In Python, Strings can be created by simply enclosing characters in quotes. Python does not support character types. These are treated as length-one strings, and are also considered as substrings. Substrings are immutable and can’t be changed once created.

Strings are the ordered blocks of text that are enclosed in single or double quotations. Thus, whatever is written in quotes, is considered as string. Though it can be written in single or double quotations, double quotation marks allow the user to extend strings over multiple lines without backslashes, which is usually the signal of continuation of an expression, e.g., ‘abc’, “ABC”.

Concatenation and Repetition

• Strings are concatenated with the +sign:

>>> ‘abc’+‘def’

‘abcdef’

• Strings are repeated with the *sign:

>>> ‘abc’*3

‘abcabcabc’

Indexing and Slicing Operation

• Python starts indexing at ‘0’
• A string s will have indexes running from 0 to len(s)-1 (where len(s) is the length of s) in integer quantities.
• S[i] fetches the ith element in s.

Built-in String Methods

Following are the built-in String Methods that can be used in Python:

• capitalize() – Capitalizes the first letter of string.
• count(str, beg= 0, end=len(string)) – Counts how many times str occurs in string or in a substring of string if beginning index ‘beg’ and ending index ‘end’ are given.
• encode(encoding=‘UTF-8’,errors=‘strict’) – Returns encoded string version of string; on error, default raises a ValueError, unless the error is given with ‘ignore’ or ‘replace’.
• decode (encoding=‘UTF-8’, errors=‘strict’) – Decodes the string using the codec registered for Encoding. Encoding defaults to the default string function.
• index(str, beg=0, end=len(string))- Same as find(), but raises an exception if str is not found.
• max(str)- Returns the max alphabetical character from the string str.
• min(str)- Returns the min alphabetical character from the string str.
• replace(old, new [, max])- Replaces all occurrences of ‘old’ in string with ‘new’ or maximum occurrences if max is given.
• upper()- Converts lowercase letters in a string to uppercase.

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