Class 3 – Monday, August 28
March on even though it's August
Together we learn — To say what we mean to say — A skill to treasure
Look both ways
Examples from last class – need to be examined more
Examples of the day – please download now
- Introduces the notion of guidelines and standard practices
- Program contains several errors that need to be fixed
- Introduces numeric types
intandfloat. They are respectively the type of values Python uses for integers and decimals.
- The Python arithmetic operators are: addition:
+; subtraction:-; multiplication:*; decimal division:/; integer division://; exponentiation:**; remaindering:%
- If one of the operands of an arithmetic operation is decimal, the result is decimal; otherwise, the result is integer except for decimal division.
- Introduces the
importstatement. By the way,importis a Python keyword. Keywords are not allowed to be used to name things. Keywords are reserved by Python for special usage. Keywordimporttells Python a module (library) is should be set up as a program resource.
- Also introduces the
.operator. The operator is typically called the dot or selection operator. The.tells Python that an element of the resource to its left is having one of its components (the one to its right) being selected for use.`
Help needed
- One of your classmates is in need of a note taker. Doing so would be a significant demonstration of class participation.
- If you take accurate and legible notes, please apply online at the Student Disability Access Center website: http://www.virginia.edu/studenthealth/sdac.html. Or, if you prefer, visit the SDAC office at the Elson Student Health Center, call 433-243-5180 or email sdac@virginia.edu.
Shape your future
- Influence the scheduling of Tests 1 and 2. It is our intention to schedule the tests on days that collectively minimze the number of other tests being taken.
- Influence the problem sets we consider this semester. It is our intention to choose problems the best we can that interest all students. It is known that faculty and student interests can differ.
Agenda
- Continue our exploration of digital problem solving
- Expand our communication and abstraction skills
- Begin an appreciation for writing readable code
- Look at our haiku gallery
- Introduce additional programming concepts
- Introduce variables
- Introduce integer and decimal operations
- Introduce additional terminology to which you should become accustomed
• Variable • Value • Operator • Decimal division • Integer division • Remainder • Mod • Type int• Type float
To do list
- Review class artifacts
- Read and Reread
- The Coder's Apprenctice : sections 3 – 4, and/or
- How to Think Like a Computer Scientist: Learning with Python 3: Sections 10.2 – 10.11
- Complete the homework
Take aways
- A video examining the insand outs of a first program
- There are two forms for the
print()function
- A
print()statement with an empty parameter list produces an empty line of output
- A
print()statement with one or more comma-separated values produces a line of output composed of the values with a single space separating one value from the next
- A literal string is a sequence of characters with in quotes (can be single or double)
- Python has two string operators
- Concatenation:
+
- Takes two strings s and t and produces a new string by first copying s and immediately following it with a copy of t
- Duplication:
*
- Takes its integer n operand and its string operand s and produces a new string that is n copies of s
- Python allows integer and decimal arithmetic operations
- Addition:
+
- Subtraction:
-
- Multiplication:
*
- Decimal division:
/
- Integer division:
//
- Exponentiation:
**
- Remaindering:
%
- If one of the operations of arithmetic operation is decimal, the result is decimal
- If an expression has more than one operation, the Python will
- First do any exponentiation operations
- Next do any multiplication, division, or remaindering operations going from left to right
- Then do any addition or subtraction operations going from left to right
- Our computers are limited in how much information they can store. Python recognizes that not all integers and decimals can be represented because there is only finite amount of memory in a machine
- Python has a type
int. This type is for representing the best it can do with integers
- Python has a type
float. This type is for representing the best it can do with decimals. With a 64-bit operating system, thefloatcan support at must 15 digits of precision
- Python has a type
str. This type is for representing sequences of charactes.