Page 367 - Computer Science V2.0 Class 11

Let's Summarise

Ø A string is a sequence of characters.
Ø Strings can be enclosed in single quotes (' '), double quotes (" "), or triple quotes (''' ''' or """ """).
Ø An escape character is a special character that is used to represent characters that are difficult to type or that
have a special meaning within strings. It is denoted by a backslash \ followed by another character.
Here are some commonly used escape characters in Python strings:
a. Newline \n: Inserts a newline character.
b. Tab \t: Inserts a tab character.
c. Backslash \\: Inserts a single backslash.
d. Single Quote \': Inserts a single quote.

e. Double Quote \": Inserts a double quote.
f. Null Character \0: Inserts a null character.
Ø To access a character in a string, use the index of the required element within square brackets.
Ø In Python, indexes for accessing string characters includes [0, len(string)-1] and [-len(string), -1].
Ø (+) operator is used to concatenate two strings.
Ø (*) operator produces a string, concatenated with itself a specified number of times.
Ø str (): To transform a data object to a string.

Ø Membership operator in returns true if a character exists in the given string.
Ø Membership operator not in returns true if a character does not exist in the given string.
Ø A slice is marked by specifying the start, finish, and step indices using the notation:
<start>:<finish>:<step>
Ø Python also provides some built-in string manipulation methods like:
len(): Returns the length of a string.
reverse (): Returns a string having characters in the reversed sequence of the original string.
s.lower(): Returns lowercase version of the string.
s.upper(): Returns uppercase version of the string.
s.title(): Returns a string which has the first letter of every word of original string converted to
uppercase, while remaining letters are converted to lowercase.
s.capitalize(): Returns a string which has all the letters in the original string converted to uppercase.
s.isupper(): Tests whether the string comprises only uppercase characters.
s.islower(): Tests whether the string comprises only lowercase characters.
s.isalpha(): Tests whether a string comprises only alphabets.
s.isdigit(): Tests whether a string comprises only digits.
s.isalnum(): Tests whether a string contains only alphabets and digits.
s.isspace(): Tests whether a string comprises only whitespace characters.
s.startswith(subStr): Tests whether the string starts with the string subStr, passed as a parameter.

s.endswith(subStr): Tests whether the string ends with the suffix subStr, passed as a parameter.
s.find(subStr): Returns the index of the first occurrence of the string passed as an argument.
s.rfind(): Returns the index of the last occurrence of a substring in the given string.
s.index(subStr): Returns the index of the first occurrence of the substring passed as an argument.
s.replace(old, new): Returns a string where all occurrences of the old string are replaced by the
new string.

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