String Operations and Indexing
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Questions and Answers

What does the method isalnum() return for the string '***&&'?

  • False (correct)
  • True
  • None
  • Error
  • Which of the following strings will return True when using the isalpha() method?

  • h221
  • hello (correct)
  • hello1
  • 123abc
  • If the string 'h221' is passed to the isdigit() method, what will be the output?

  • True
  • None
  • Error
  • False (correct)
  • What will the islower() method return for the string 'Abc'?

    <p>False (A)</p> Signup and view all the answers

    For the string ' ', what will the isspace() method return?

    <p>True (B)</p> Signup and view all the answers

    What does the method lstrip() do?

    <p>Removes leading spaces from a string. (C)</p> Signup and view all the answers

    What would be the output of str.lstrip('Py') if str = 'Python Program'?

    <p>'thon Program' (B)</p> Signup and view all the answers

    Which of the following methods removes trailing whitespace from a string?

    <p>rstrip() (B)</p> Signup and view all the answers

    If str = ' Green Revolution ', what does str.strip() return?

    <p>'Green Revolution' (A)</p> Signup and view all the answers

    What output does the command st.rstrip('ser') return for st = 'Computers'?

    <p>'Comput' (C)</p> Signup and view all the answers

    What does the first code segment count in the input string?

    <p>Number of words starting with vowels (C)</p> Signup and view all the answers

    In the second code segment, what is stored in the variable 'lword'?

    <p>The longest word in the string (D)</p> Signup and view all the answers

    What logical structure does the third code segment utilize to check if a string is a palindrome?

    <p>A for loop that inspects each character (B)</p> Signup and view all the answers

    In the string transformation example, what happens to uppercase letters at even indices?

    <p>They are converted to lowercase (D)</p> Signup and view all the answers

    What is the final output of the string MyText after the transformation process?

    <p>@Ae@cCdDIie (B)</p> Signup and view all the answers

    What does the find() function return when the substring is not found in the string?

    <p>-1 (D)</p> Signup and view all the answers

    What will be the result of the expression 'hello'.find('l', 3)?

    <p>3 (C)</p> Signup and view all the answers

    Which statement correctly describes the behavior of the index() function?

    <p>It raises an exception if the substring is not found. (A)</p> Signup and view all the answers

    What does the endswith() function return when the specified substring matches the end of the string?

    <p>True (B)</p> Signup and view all the answers

    Which of the following will yield False when checked with startswith() for the string 'Machine Learning'?

    <p>Learning (D)</p> Signup and view all the answers

    If the input string is 'hello', what will the output be for str.isalnum()?

    <p>True (C)</p> Signup and view all the answers

    What will str.count('Hello') return if the string is 'Hello, Hello, hello'?

    <p>1 (B)</p> Signup and view all the answers

    Which of the following statements about the isalnum() function is correct?

    <p>It does not check for spaces or special characters. (D)</p> Signup and view all the answers

    What will be the output of the expression ord('C')?

    <p>67 (D)</p> Signup and view all the answers

    What does the split() method do when the input is 'apple,banana,cherry' with a separator of ','?

    <p>Returns a list ['apple', 'banana', 'cherry'] (C)</p> Signup and view all the answers

    When using the toggle case method on the string 'Hello World!', what will be the output?

    <p>hELLO wORLD! (C)</p> Signup and view all the answers

    What does the expression str1[2:6] return for the string 'HAPPINESS'?

    <p>PPIN (D)</p> Signup and view all the answers

    How many spaces will be counted by the program that inputs the string 'This is a test'?

    <p>2 (B)</p> Signup and view all the answers

    What will the output be if the function is called with the argument chr(97)?

    <p>'a' (D)</p> Signup and view all the answers

    In Python, how can you create an immutable string?

    <p>Once created, strings cannot be changed. (B)</p> Signup and view all the answers

    What is the result of running the program that replaces spaces with hyphens on the input 'Python is fun'?

    <p>Python-is-fun (C)</p> Signup and view all the answers

    Which of the following escape sequences represents a tab in a string?

    <p>\t (B)</p> Signup and view all the answers

    Which string will be returned by the function that removes capital vowels from the string 'Beautiful Day'?

    <p>eautiful Day (B)</p> Signup and view all the answers

    What will the output be for the expression x[1:6:2] when x='COmpUtER'?

    <p>OPT (B)</p> Signup and view all the answers

    What will happen if you try to assign a new value directly to a string variable like St1 = 't' after declaring St1 = 'Information'?

    <p>It will result in an error. (C)</p> Signup and view all the answers

    What does the program count when it is tasked with counting how many words start with vowels in the string 'An apple a day'?

    <p>3 (B)</p> Signup and view all the answers

    What does the output of print(x[-1]) return when x='COmpUtER'?

    <p>R (D)</p> Signup and view all the answers

    Which of the following correctly assigns the message 'Hello, "How are you"?' to a variable in Python?

    <p>str = 'Hello, &quot;How are you&quot;?' (B)</p> Signup and view all the answers

    What does the expression print(str1[-3:-8:-1]) return when str1='HAPPINESS'?

    <p>ENIPP (D)</p> Signup and view all the answers

    Flashcards

    What is a string?

    A sequence of characters enclosed within quotes (single, double, or triple).

    What is indexing in strings?

    Each character in a string has a unique index (position). Positive indices start from 0 for the first character and increase to the right. Negative indices start from -1 for the last character and decrease to the left.

    How do you slice strings?

    You can retrieve specific characters or substrings using the slicing notation [start:end:step] with these indices.

    What is meant by strings being immutable?

    Strings in Python are immutable, meaning they cannot be directly modified once created.

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    Escape Sequences in strings

    You can use escape sequences like \n for a new line, \t for a tab, \" for a double quote, and \' for a single quote to represent special characters within a string.

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    String Operations

    You can perform various operations on strings, including addition and multiplication. String multiplication concatenates a string multiple times, while string addition joins strings together.

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    Explain string slicing using [start:end:step]

    In string indexing, [start:end:step] selects characters from the string. start is the index of the first character, end is the index of the last character (not included), and step defines the increment between characters.

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    How can you modify an existing string?

    In Python, you cannot modify characters directly within a string as it is immutable. You can, however, create a completely new string by concatenating the desired changes using operators or string methods.

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    What does the isspace() function do?

    The isspace() function checks whether all characters in a string are whitespace characters (spaces, tabs, newlines). It returns True if all characters are whitespace, and False otherwise.

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    What is lstrip()?

    The lstrip() function removes leading whitespace characters from the left side of a string. It returns a new string with the leading whitespace removed.

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    What is rstrip()?

    The rstrip() function removes trailing whitespace characters from the right side of a string. It returns a new string with the trailing whitespace removed.

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    What is strip()?

    The strip() function removes both leading and trailing whitespace characters from a string. It returns a new string with the whitespace removed from both ends.

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    Can strip() remove more than just whitespace?

    The strip() function can remove characters other than whitespace by specifying a string argument to the function. The characters in the argument string will be removed from the beginning and end of the string.

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    String

    A sequence of characters. Examples include "hello" or "123"

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    count()

    Counts how many times a substring appears within a string

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    find()

    Finds the index of the first occurrence of a substring within a string. Returns -1 if not found.

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    index()

    Similar to find(), but raises an exception if the substring is not found.

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    startswith()

    Checks if a string starts with a specified substring. Returns True or False.

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    endswith()

    Checks if a string ends with a specified substring. Returns True or False.

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    isalnum()

    Checks if a string contains only alphanumeric characters (letters and numbers). Returns True or False.

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    isidentifier()

    Checks if a string is a valid Python identifier. Avoids keywords and starts with a letter or underscore. Returns True or False

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    isalpha()

    This method checks if every character in a string is a letter (a-z, A-Z) and returns True if it is, otherwise it returns False.

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    isdigit()

    A function that accepts a string as input and returns True if the string contains only digits (0-9) and False otherwise.

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    islower()

    This string method checks if all characters in a string are lowercase and returns True if they are, otherwise it returns False.

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    isupper()

    This Python string method returns True if all characters in a string are uppercase and False otherwise.

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    count() Function

    A function that returns the number of occurrences of a substring within a string.

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    startswith() Function

    Determines if a string begins with a specified substring. Returns True if it does, False otherwise.

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    endswith() Function

    Determines if a string ends with a specified substring. Returns True if it does, False otherwise.

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    isalnum() Function

    Examines a string to see if it contains only alphanumeric characters (letters and numbers). Returns True if so, False otherwise.

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    What does the split() method do?

    The split() method breaks a string into a list of substrings based on a specified separator. If no separator is provided, it splits at whitespace.

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    Explain the purpose of the ord() function.

    The ord() function converts a single character to its corresponding ASCII or Unicode numerical value. This value represents the position of the character within the ASCII/Unicode table.

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    What does the chr() function do?

    The chr() function converts an integer value representing an ASCII or Unicode code point back into its corresponding character. It finds the character associated with a specific code.

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    Describe the Python code to count spaces in a string.

    This program takes a string as input and counts the number of spaces present in it.

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    What does the Python code do to toggle the string's case?

    The code takes a string as input and converts it to toggle case, switching uppercase characters to lowercase and vice versa.

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    Explain the Python code that replaces spaces with hyphens in a string.

    This program takes a string as input and replaces all spaces within the string with hyphens.

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    What does the Python code do to remove capital vowels from a string?

    This code takes a string as input and generates a new string without any capitalized vowels.

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    Study Notes

    String Indexing

    • Strings are sequences of characters.
    • Characters are indexed using positive integers (left to right) or negative integers (right to left).
    • The first character has index 0.
    • Negative indices count from the end of the string (-1 for the last character).

    String Immutability

    • Strings are immutable data types.
    • Once a string is created, it cannot be changed.
    • Trying to modify a character in a string results in an error.

    String Operations

    • Concatenation: Joining strings together.
    • Repetition: Repeating a string a certain number of times.
    • Membership: Checking if a character or substring is part of a string (returns True or False).

    String Slicing

    • Slicing extracts parts of a string.
    • General format: str[startIndex:endIndex].
    • startIndex is inclusive, endIndex is exclusive.
    • Omitting startIndex starts from the beginning.
    • Omitting endIndex goes to the end.

    Built-in String Functions

    • len(): Returns the length of a string.
    • capitalize(): Capitalizes the first letter of a string.
    • title(): Capitalizes the first letter of each word in a string.
    • lower(): Converts a string to lowercase.
    • upper(): Converts a string to uppercase.
    • count(): Counts the occurrences of a substring in a string (can include start and end indices).
    • find(): Finds the index of the first occurrence of a substring (returns -1 if not found).
    • index(): Similar to find(), but raises an exception if the substring is not found.
    • startswith(): Checks if a string starts with a specified substring (returns True or False).
    • endswith(): Checks if a string ends with a specified substring (returns True or False).
    • isalnum(): Checks if a string consists of alphanumeric characters (returns True or False).
    • isalpha(): Checks if a string consists only of alphabets (returns True or False).
    • isdigit(): Checks if a string consists only of digits (returns True or False).
    • islower(): Checks if a string consists only of lowercase letters (returns True or False).
    • isupper(): Checks if a string consists only of uppercase letters (returns True or False).
    • isspace(): Checks if a string consists only of whitespace characters (returns True or False).
    • lstrip(): Removes leading whitespace characters.
    • rstrip(): Removes trailing whitespace characters.
    • strip(): Removes both leading and trailing whitespace characters.
    • split(): Splits a string into a list of substrings based on a separator.
    • ord(): Returns the ASCII/Unicode value of a character.
    • chr(): Returns the character corresponding to a given ASCII/Unicode value.

    String Programs

    • Various programs demonstrate string manipulations including counting spaces, toggling case, replacing spaces with hyphens, removing capital vowels and more.

    Escape Sequences

    • Used to represent special characters within strings using backslashes.
      • \n (newline)
      • \t (tab)
      • \" (double quote)
      • \' (single quote)

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    Description

    This quiz covers essential concepts of string indexing, immutability, and various string operations in programming. It includes topics such as concatenation, repetition, and slicing, providing a thorough understanding of how strings function in code. Test your knowledge on built-in string functions and their applications.

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