Class 39 — Monday November 23

I know that you know that

Programming basics — You achieved this semester — Bask in the success

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Look both ways

• Back and ahead

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Agenda

• Be chrestohistorical

• Answer questions

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Final

• If you want to take the final, you must fill out this form before 5 PM on Thanskgiving

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Thanks to the TAs for making the course successful

Katherine Brickley	Ann Hoang	Rachel McNamara	MaryJeanine Seaman
Ryan Green	Hallie Khoung	Jimmy Njuguna	Jacob St. Martin
Nadia Hassan	Kevin Luk

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Want to be a TA for CS 1112

• Departmental application

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Test problem solving process

• Read entire problem before coding

• Think about solution stratgey before coding

• Is a choice being made?

• Likely need an if-elif-else statement

• Is something be built? If so,

• Likely need an accumulator and a loop structure

• Initialize accumulator

• total = 0 for summation

• product = 1 for product

• values = [] for list

• mappings = {} for dictionary

• Loop to update accumulator

• Is a sequence just being examined?

• A loop is probably necessary unless there are built-in functions to assist (e.g., max(), min(), and len()).

for value in sequence :

  ...

• Are the elements of a simple sequence being modified?

• A for i in range loop is probably necessary.

n = len( sequence )

for i in range( 0, n ) :

  value = sequence[ i ]

  ...

  sequence[ i ] = ...

• When is a nested loop necessary? The major examples are images and datasets. Otherwise, look for a solution without nested loops first.

• Examining an image

for x in range( 0, width ) :

  for y in range( 0, height ) :

  spot = (x, y )

  ...

• Examining a dataset / table

for row in dataset :

  for value in row :

  ...

• How to check whether all elements in a sequence have a property.

• Guess True, check if any element does not.

result = True

for v in values :

  if v does not have the property

  result = False

  break

• How to check whether any elements in a sequence has a property.

• Guess False, check if any element does not.

result = False

for v in values :

  if v has the property

  result = True

  break

• How to check for the best element in a sequence

• Use built-in function max() or min(), if appropriate

• Otherwise, guess first element and check other elements to see if their better.

result = values[ 0 ]

for v in values :

  if v is better than the result

  result = v

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Other patterns

• Examine and create dictionaries

• Convert a list of tuples into a dictionary

• Convert a list of two-element lists into a dictionary

• Examine a list with respect to a dictionary

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• Examine a table

• Perform an accumulation

• Process a table on a row by row basis

• Convert cells from strings to numerics

• Check to see if all data cells in the table are of the same form

• Check to see if any data cells in the table are of the desired form

• Check to see if all rows in the table are of the same form

• Check to see if any rows in the table are of the desired form

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• Photo manipulation

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Realizations

• A variable has an identity and a type

• The identity of a variable indicates where the object which it represents can be found

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• Strings are immutable

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• Converting string data to numeric data.

• To get a single integer value nbr from a single numeric representation v

nbr = int( v )

• To get a list of integer values nbrs from a list of numeric representations

nbrs = []

for v in s :

  nbr = int( v )

  nbrs.append( nbr )

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• Python function usage

• A function invocation cannot change the identity of an argument

• All functions return a value either explicitly or implicitly. If there is no explicit return, None is returned.

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Truisms

• The test will cummulative.

• Questions can require in part familiarity with

• Using input() function

• Implementing programs and modules

• Analyzing code

• Fundamental types; e.g., int, float, and str

• Arithmetic operators; e.g., +, -, *, **, /, //, and %

• Identifiers, keywords, variables, objects, values, and references

• Logical and relational operators; and, or, not, ==, !=, <, >, <=, and >=

• Control constructs; e.g., if, for, and while

• Nested for constructs

• Random value manipulation

• random.seed()

• random.randrange()

• random.choice()

• Builtin-in functions; e.g., print(), input(), int(), float(), str(), max(), min(), len(), type(), and id()

• URLs and web files; e.g., numeric, text and CSV contents

• Ranges

• Data structures and their use: list, dict, tuples, methods and slicing

• Functions, parameters, definitions, and invocations

• Colors and PIL Image

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Final thought

• I say thanks to you — Your presence is a great gift — Brings me happiness

 

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© 2020 Jim Cohoon

Resources from previous semesters are available.