Chapter 3 : Strings

The string is a data type in Python.

A string is a sequence of characters enclosed in quotes.

We can primarily, write a string in three ways:

  1. Single quoted strings : a = ‘harry’
  2. Double quoted strings : b = “harry”
  3. Triple quoted strings : c = ”’harry”’

String Slicing:

A string in Python can be sliced for getting a part of the string.

Consider the following string:

The index in a string starts from 0 to (length-1) in Python. In order to slice a string, we use the following syntax:

Negative Indices:
Negative indices can also be used as shown in the figure above. -1 corresponds to the (length-1) index, -2 to (length-2).

Slicing with skip value

We can provide a skip value as a part of our slice like this:

word = “amazing”

word[1:6:2] # It will return ’mzn’

Other advanced slicing techniques

word = ‘amazing’

word[:7] or word[0:7] #It will return ‘amazing’

word[0:] or word[0:7] #It will return ‘amazing’

String Functions

Some of the mostly used functions to perform operations on or manipulate strings are:

  1. len() function : It returns the length of the string.

len(‘harry’) #Returns 5

  1. endswith(“rry”) : This function tells whether the variable string ends with the string “rry” or not. If string is “harry”, it returns for “rry” since harry ends with rry.
  2. count(“c”) : It counts the total number of occurrences of any character.
  3. capitalize() : This function capitalizes the first character of a given string.
  4. find(word) : This function finds a word and returns the index of first occurrence of that word in the string.
  5. replace(oldword, newword) : This function replaces the old word with the new word in the entire string.

Escape Sequence Characters:

Sequence of characters after backslash ‘\’ [Escape Sequence Characters]

Escape Sequence Characters comprises of more than one character but represents one character when used within the string.

Examples: \n (new line), \t (tab), \’ (single quote), \\ (backslash), etc.

Chapter 3 – Practice Set

  1. Write a Python program to display a user-entered name followed by Good Afternoon using input() function.
  2. Write a program to fill in a letter template given below with name and date.

letter = ‘’’ Dear <|NAME|>,

You are selected!

<|DATE|>

  1. Write a program to detect double spaces in a string.
  2. Replace the double spaces from problem 3 with single spaces.
  3. Write a program to format the following letter using escape sequence characters.

letter = “Dear Harry, This Python course in nice. Thanks!!”