Chapter 5: Iteration

Flashcards covering key concepts from Chapter 5 on Iteration, including updating variables, while statements, loop patterns, and debugging.

Updating Variables

A common pattern in assignment statements where the new value depends on the old, such as x = x + 1. Requires initialization before updating.

Increment

Updating a variable by adding 1.

Decrement

Updating a variable by subtracting 1.

While Statement

A Python language feature for iteration that repeats a block of code as long as a condition is true.

Iteration

Each execution of the body of a loop.

Iteration Variable

The variable that changes each time the loop executes and controls when the loop finishes.

Infinite Loop

A loop that repeats forever because there is no iteration variable or the terminating condition is never satisfied.

Break Statement

A statement used to jump out of a loop, typically used in infinite loops when an exit condition is met.

Continue Statement

A statement used to skip the current iteration of a loop and jump to the next iteration.

Definite Loop (For Loop)

A loop that iterates through a known set of items, such as a list of words, lines in a file, or a list of numbers.

Indefinite Loop (While Loop)

A loop that continues until some condition becomes False.

Loop Patterns

Common structures for looping through items to find something, like the largest or smallest value.

Counting Loop

A loop that counts the number of items in a list.

Summing Loop

A loop that computes the total of a set of numbers.

Accumulator

A variable used in a loop to add up or accumulate a result.

Maximum/Minimum Loops

Loops designed to find the largest or smallest value in a list or sequence.

None

A special constant value in Python used to mark a variable as 'empty'.

Debugging by Bisection

A debugging technique where you break the program in half to isolate the source of an error.

Counter

A variable used in a loop to count the number of times something happened, initialized to zero and incremented each time.

Initialize

Assigning an initial value to a variable before it is updated in a program.

Infinite loop info

How to avoid : make sure loop control variable is in header (ie while i<= 10: - i is loop ctrl variable , if its not in he header it will continue to infinity)

While loop using boolean operators

poop=0

while not poop xxx: (this means while poop is true cuz poop variable is defined as false) (0 means false)

i

i is a common LOOP CONTROL VARIABLE

How to choose which loop to use

• When you know the number of iterations

 use a counter-controlled or definite loop such as “for”

• When the iterations depend on a condition

 use a conditional or indefinite loop such as “while”

Is and Is not operators

‘Is’ operator means ‘is the same as’

‘Is not’

How to know what itertion variable to use and when

When you know how many times you want the thing to = for

when you want something to keep going UNTIL something happens = while

ranges

range(stop) - goes from 0 , stops 1 before the stop

range(start,stop) - goes from start to 1 before stop

range(start,stop,+- step)- goes from start to 1 before stop , increases/decreases by step each time

odd/even .py

• Add +1 at the end of the range to make python iterate the full range number , not just stop one before

• to see is something is even - n %2 (returns a remainder)== 0 obvi if its even theres no remainder

constants

variable name in all caps , BIG_FORHEAD = 5 ; Python recognizes this as a constant.

Break vs continue

Continue - means if x== 5 , pass by ie dont use this , like ignore it and go to the next one

break , if x==5 , stop executing the loop entirely.