Python for Loops

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Questions and Answers

A `for` loop in Python is an example of a control statement that most easily supports indefinite iteration.

False (B)

In a `for` loop, the first line of code (e.g., `for i in range(5):`) is referred to as the loop body.

False (B)

If the exponent is a positive integer, the loop body in an exponentiation computation will not be executed, and the product would remain as 1.

False (B)

In Python, `range(1, 5)` includes the lower bound (1) but excludes the upper bound (5).

True (A) Signup and view all the answers

The augmented assignment `x += 5` is equivalent to `x + 5 = x`.

False (B) Signup and view all the answers

An off-by-one error in a loop is identified as a syntax error by the Python interpreter.

False (B) Signup and view all the answers

In Python, the `range()` function returns a tuple.

False (B) Signup and view all the answers

You cannot specify a step value with the `range()` function.

False (B) Signup and view all the answers

A loop that counts down must have a positive step value in the `range` function.

False (B) Signup and view all the answers

In formatted output, the field width refers to the amount of space reserved to display a data value.

True (A) Signup and view all the answers

When formatting floating-point numbers, it's impossible to specify the number of digits after the decimal point.

False (B) Signup and view all the answers

Selection statements allow a program to execute code in a linear, non-conditional fashion.

False (B) Signup and view all the answers

In Python, the boolean expression `5 = 5` will evaluate to `True`.

False (B) Signup and view all the answers

The `if-else` statement is a two-way selection construct, meaning you can only check for at most two different conditions.

False (B) Signup and view all the answers

A multi-way `if` statement must always include an `else` clause to handle all possible conditions.

False (B) Signup and view all the answers

In a compound boolean expression, the `and` operator returns `True` if at least one of the conditions is `True`.

False (B) Signup and view all the answers

The `not` operator inverts the truth value of its operand; `not True` evaluates to `True`.

False (B) Signup and view all the answers

Short-circuit evaluation means that in a compound Boolean expression, Python evaluates all the expressions regardless of the outcome of the first expressions.

False (B) Signup and view all the answers

A `while` loop describes definitive iteration.

False (B) Signup and view all the answers

A `while` loop is also known as a post-test loop.

False (B) Signup and view all the answers

The statements inside a `while` loop are guaranteed to execute at least once.

False (B) Signup and view all the answers

The loop control variable in a `while` loop is initialized within the loop body.

False (B) Signup and view all the answers

A `for` loop can always be directly converted into an equivalent `while` loop.

True (A) Signup and view all the answers

An infinite loop occurs when the continuation condition will eventually return false.

False (B) Signup and view all the answers

The `break` statement provides a way to exit a loop, but only if it's nested inside a selection statement.

False (B) Signup and view all the answers

The module `random` is used for generating random numbers.

True (A) Signup and view all the answers

`random.randint(a, b)` returns a random integer excluding both `a` and `b`.

False (B) Signup and view all the answers

Control statements determine the order in which statements are expressed in a program.

False (B) Signup and view all the answers

Definite iteration involves executing a set of statements a number of times that is determined during runtime.

False (B) Signup and view all the answers

The `for` loop consists of a header and a tail, which mark the beginning and end of the loop's execution.

False (B) Signup and view all the answers

The `for` loop is not suitable for implementing count-controlled loops.

False (B) Signup and view all the answers

Python uses short-circuit evolution for compound Boolean expressions.

False (B) Signup and view all the answers

Selection statements prevent a program from making choices based on conditions.

False (B) Signup and view all the answers

The `if-elif` statement only handles a single condition.

False (B) Signup and view all the answers

Conditional iteration involves executing statements while an expression resolves to false.

False (B) Signup and view all the answers

The `while` loop checks a condition at the end of the loop body.

False (B) Signup and view all the answers

A `break` statement allows to skip over a code block if the respective condition turns out true.

False (B) Signup and view all the answers

The `for` loop cannot be converted to a `while` loop under any circumstances.

False (B) Signup and view all the answers

An infinite loop always will result in an error.

False (B) Signup and view all the answers

The function call `random.randint` returns a floating point number.

False (B) Signup and view all the answers

In Python, the `for` loop is considered an exit-controlled loop because it relies on a condition to determine if another iteration is required.

False (B) Signup and view all the answers

The `range` function in Python, when used with a `for` loop, can only count upwards and not downwards through a sequence of numbers.

False (B) Signup and view all the answers

In a multi-way selection statement, if none of the `elif` conditions are met, the `else` block will execute, and if the `else` block is omitted, the program will terminate with an error.

False (B) Signup and view all the answers

In Python, the logical operator `not` has a lower precedence compared to the logical operators `and` and `or`.

False (B) Signup and view all the answers

A `break` statement is designed to terminate the entire program execution, whereas the `continue` statement only skips the current iteration of a loop.

False (B) Signup and view all the answers

Flashcards

Repetition Statements (Loops)

Statements that repeat an action in programming.

Iteration

Each execution of the action within a loop.

Definite Iteration

Loops that repeat an action a predefined number of times.

Indefinite Iteration

Loops that perform an action until the program decides to stop.

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For Loop

A control statement that supports definite iteration.

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Loop Header

The first line of a for loop, specifying the loop's parameters.

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Loop Body

The code that is executed repeatedly in a loop.

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Off-by-One Error

An error where a loop executes one too many or one too few times.

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Traversing a Sequence

Visiting each value in a sequence.

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Range function

A Python function that returns a sequence of numbers.

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Augmented Assignment

Combining an arithmetic or concatenation operator with the assignment symbol.

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Selection Statements

Statements that allow a computer to make choices based on conditions.

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Boolean Data Type

A data type with two possible values: True and False.

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If Statement

A statement that executes a block of code if a condition is true.

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If-Else Statement

A two-way selection statement.

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Multi-Way If Statement

A selection statement with more than two alternative courses of action.

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Logical Operators

Operators used to create complex conditions.

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Short-Circuit Evaluation

Evaluation that stops as soon as the result is known.

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While Loop

Can be used to describe conditional iteration.

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Continuation Condition

Condition tested within a loop to determine if it should continue.

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Infinite Loop

A loop that runs indefinitely because its continuation condition never becomes false.

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Entry-Control Loop

A loop that checks its condition at the beginning.

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Loop Control Variable

The variable checked in a loop condition.

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Break Statement

Causes an exit from the loop.

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random.randint()

Returns a random number between inputs.

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Field width

Total number of data characters and additional spaces for a datum in a formatted string

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Study Notes

Objectives

Write a loop to repeat actions a fixed number of times.
Construct a loop to traverse characters in a string.
Learn to write loops that count up and loops that count down.
The objective is to write entry-controlled loops halting on a false condition.
Utilize selection statements to implement choices in a program.
Construct conditions for condition-controlled loops and selection statements.
Use logical operators to develop compound Boolean expressions.
Use a selection statement and a break statement to exit non-entry-controlled loops.

Definitive Iteration: The for Loop

Repetition statements, known as loops, repeat an action.
Each instance of an action’s repetition is a pass or iteration.
Definite iteration loops repeat an action over a predefined number of times.
Indefinite iteration loops perform an action until the program concludes it should halt.

Executing a Statement a Given Number of Times

The for loop most easily supports definite iteration.
The basic structure includes a variable that iterates through a range: for <variable> in range(<an integer expression>):
The first line of code within a for loop is called the loop header.
The remaining code is known as the loop body, which must be be indented and aligned in same tab space.

Loop and Computation Example

The code below computes an exponentiation for a non-negative exponent
Below is a code example

>>> exponent = 3
>>> product = 1
>>> for eachPass in range(exponent):
product = product * number
print(product, end = " ")
2 4 8
>>> product
8

If the exponent were 0, the loop body would not execute, and the value of product would remain 1.

Count-Controlled Loops

Count-controlled loops iterate through a range of numbers.
To specify an explicit lower bound, use a range with two arguments, range(lower_bound, upper_bound).

Enhanced Summation Example

The code below is an example of bound-delimited summation

>>> lower = int(input("Enter the lower bound: "))
Enter the lower bound: 1
>>> upper = int(input(“Enter the upper bound: "))
Enter the upper bound: 10

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Description

Learn how to write loops in Python to repeat actions a fixed number of times. Understand definite and indefinite iteration and how to implement choices and control loop conditions using selection statements and logical operators.

Python for Loops

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Podcast

Questions and Answers

A for loop in Python is an example of a control statement that most easily supports indefinite iteration.

In a for loop, the first line of code (e.g., for i in range(5):) is referred to as the loop body.

If the exponent is a positive integer, the loop body in an exponentiation computation will not be executed, and the product would remain as 1.

In Python, range(1, 5) includes the lower bound (1) but excludes the upper bound (5).

The augmented assignment x += 5 is equivalent to x + 5 = x.

An off-by-one error in a loop is identified as a syntax error by the Python interpreter.

In Python, the range() function returns a tuple.

You cannot specify a step value with the range() function.

A loop that counts down must have a positive step value in the range function.

In formatted output, the field width refers to the amount of space reserved to display a data value.

When formatting floating-point numbers, it's impossible to specify the number of digits after the decimal point.

Selection statements allow a program to execute code in a linear, non-conditional fashion.

In Python, the boolean expression 5 = 5 will evaluate to True.

The if-else statement is a two-way selection construct, meaning you can only check for at most two different conditions.

A multi-way if statement must always include an else clause to handle all possible conditions.

In a compound boolean expression, the and operator returns True if at least one of the conditions is True.

The not operator inverts the truth value of its operand; not True evaluates to True.

Short-circuit evaluation means that in a compound Boolean expression, Python evaluates all the expressions regardless of the outcome of the first expressions.

A while loop describes definitive iteration.

A while loop is also known as a post-test loop.

The statements inside a while loop are guaranteed to execute at least once.

The loop control variable in a while loop is initialized within the loop body.

A for loop can always be directly converted into an equivalent while loop.

An infinite loop occurs when the continuation condition will eventually return false.

The break statement provides a way to exit a loop, but only if it's nested inside a selection statement.

The module random is used for generating random numbers.

random.randint(a, b) returns a random integer excluding both a and b.

Control statements determine the order in which statements are expressed in a program.

Definite iteration involves executing a set of statements a number of times that is determined during runtime.

The for loop consists of a header and a tail, which mark the beginning and end of the loop's execution.

The for loop is not suitable for implementing count-controlled loops.

Python uses short-circuit evolution for compound Boolean expressions.

Selection statements prevent a program from making choices based on conditions.

The if-elif statement only handles a single condition.

Conditional iteration involves executing statements while an expression resolves to false.

The while loop checks a condition at the end of the loop body.

A break statement allows to skip over a code block if the respective condition turns out true.

The for loop cannot be converted to a while loop under any circumstances.

An infinite loop always will result in an error.

The function call random.randint returns a floating point number.

In Python, the for loop is considered an exit-controlled loop because it relies on a condition to determine if another iteration is required.

The range function in Python, when used with a for loop, can only count upwards and not downwards through a sequence of numbers.

In a multi-way selection statement, if none of the elif conditions are met, the else block will execute, and if the else block is omitted, the program will terminate with an error.

In Python, the logical operator not has a lower precedence compared to the logical operators and and or.

A break statement is designed to terminate the entire program execution, whereas the continue statement only skips the current iteration of a loop.

Flashcards

Repetition Statements (Loops)

Iteration

Definite Iteration

Indefinite Iteration

For Loop

Loop Header

Loop Body

Off-by-One Error

Traversing a Sequence

Range function

Augmented Assignment

Selection Statements

Boolean Data Type

If Statement

If-Else Statement

Multi-Way If Statement

Logical Operators

Short-Circuit Evaluation

While Loop

Continuation Condition

Infinite Loop

Entry-Control Loop

Loop Control Variable

Break Statement

random.randint()

Field width

Study Notes

Objectives

Definitive Iteration: The for Loop

Executing a Statement a Given Number of Times

A `for` loop in Python is an example of a control statement that most easily supports indefinite iteration.

In a `for` loop, the first line of code (e.g., `for i in range(5):`) is referred to as the loop body.

In Python, `range(1, 5)` includes the lower bound (1) but excludes the upper bound (5).

The augmented assignment `x += 5` is equivalent to `x + 5 = x`.

In Python, the `range()` function returns a tuple.

You cannot specify a step value with the `range()` function.

A loop that counts down must have a positive step value in the `range` function.

In Python, the boolean expression `5 = 5` will evaluate to `True`.

The `if-else` statement is a two-way selection construct, meaning you can only check for at most two different conditions.

A multi-way `if` statement must always include an `else` clause to handle all possible conditions.

In a compound boolean expression, the `and` operator returns `True` if at least one of the conditions is `True`.

The `not` operator inverts the truth value of its operand; `not True` evaluates to `True`.

A `while` loop describes definitive iteration.

A `while` loop is also known as a post-test loop.

The statements inside a `while` loop are guaranteed to execute at least once.

The loop control variable in a `while` loop is initialized within the loop body.

A `for` loop can always be directly converted into an equivalent `while` loop.

The `break` statement provides a way to exit a loop, but only if it's nested inside a selection statement.

The module `random` is used for generating random numbers.

`random.randint(a, b)` returns a random integer excluding both `a` and `b`.

The `for` loop consists of a header and a tail, which mark the beginning and end of the loop's execution.

The `for` loop is not suitable for implementing count-controlled loops.

The `if-elif` statement only handles a single condition.

The `while` loop checks a condition at the end of the loop body.

A `break` statement allows to skip over a code block if the respective condition turns out true.

The `for` loop cannot be converted to a `while` loop under any circumstances.

The function call `random.randint` returns a floating point number.

In Python, the `for` loop is considered an exit-controlled loop because it relies on a condition to determine if another iteration is required.

The `range` function in Python, when used with a `for` loop, can only count upwards and not downwards through a sequence of numbers.

In a multi-way selection statement, if none of the `elif` conditions are met, the `else` block will execute, and if the `else` block is omitted, the program will terminate with an error.

In Python, the logical operator `not` has a lower precedence compared to the logical operators `and` and `or`.

A `break` statement is designed to terminate the entire program execution, whereas the `continue` statement only skips the current iteration of a loop.