Course Overview Python Basics Course Slides
- 2. About Your Instructors Walker White Dietrich Geisler • New instructor § Taught 1110 this summer § First time with a large class • Will be back next week 8/22/22 Overview, Types & Expressions 2 • Director: GDIAC § Game Design @ Cornell § Game courses in Spring • Teach CS 1110 in fall
- 3. We Are (Essentially) Full! • Lecture times are somewhat flexible. § Technically have room for ~50 in each § We can use this to swap lectures • Labs/sections at fire code capacity § We lost ACCEL labs last years § New classrooms are not as flexible • But lots of drops; watch Student Center! 8/22/22 Overview, Types & Expressions 3
- 4. CS 1110 Fall 2022 • Outcomes: § Fluency in (Python) procedural programming • Usage of assignments, conditionals, and loops • Ability read and test programs from specifications § Competency in object-oriented programming • Ability to recognize and use objects and classes § Knowledge of searching and sorting algorithms • Knowledge of basics of vector computation • Website: § www.cs.cornell.edu/courses/cs1110/2022fa/ 4 8/22/22 Overview, Types & Expressions
- 5. Intro Programming Classes Compared CS 1110: Python • No prior programming experience necessary • No calculus • Slight focus on § Software engineering § Application design CS 1112: Matlab • No prior programming experience necessary • One semester of calculus • Slight focus on § Scientific computation § Engineering applications 5 8/22/22 Overview, Types & Expressions But either course serves as a pre-requisite to CS 2110
- 6. CS 1133: Short Course in Python • 2-credit course in how to use Python § Material is roughly the first half of CS 1110 § Most of the Python of 1110, but not theory § Two assignments; no exams § No experience required • This is the only way to take Python S/U § CS 1110 is no longer offered S/U (in fall) § Best for students that just want Python 8/22/22 Overview, Types & Expressions 6
- 7. Why Programming in Python? • Python is easier for beginners § A lot less to learn before you start “doing” § Designed with “rapid prototyping” in mind • Python is more relevant to non-CS majors § NumPy and SciPy heavily used by scientists • Python is a more modern language § Popular for web applications (e.g. Facebook apps) § Also applicable to mobile app development 8/22/22 Overview, Types & Expressions 7
- 8. Class Structure • Lectures. Every Tuesday/Thursday § Not just slides; interactive demos almost every lecture § Because of enrollment, please stay with your section § Semi-Mandatory. 1% Participation grade from iClickers • Section/labs. Phillips 318 or Hollister 401 § Guided exercises with TAs and consultants helping out • Meets Tuesday/Thursday or Wednesday/Friday • Only Phillips 318 has computers (bring your laptop) § Contact Amy (ahf42@cornell.edu) for section conflicts § Mandatory. Missing more than 3 lowers your final grade 8 8/22/22 Overview, Types & Expressions
- 9. Class Structure • Lectures. Every Tuesday/Thursday § Not just slides; interactive demos almost every lecture § Because of enrollment, please stay with your section § Semi-Mandatory. 1% Participation grade from iClickers • Section/labs. Phillips 318 or Hollister 401 § Guided exercises with TAs and consultants helping out • Meets Tuesday/Thursday or Wednesday/Friday • Only Phillips 318 has computers (bring your laptop) § Contact Amy (ahf42@cornell.edu) for section conflicts § Mandatory. Missing more than 2 lowers your final grade 9 8/22/22 Overview, Types & Expressions All Labs will be use the online system. But they are not intended to be “online”.
- 10. Is there a TextBook? No 8/22/22 Overview, Types & Expressions 10
- 11. Is there a TextBook? No 8/22/22 Overview, Types & Expressions 11 The asynchronous videos are essentially the textbook
- 12. What Do I Need for this Class? • Laptop Computer § Capable of running Python (no ChromeBooks!) § Minimum of 8Gb of RAM • Python Installation § Will be using the latest Anaconda version § See instructions on website for how to install • iClicker. Acquire by next Tuesday § Credit for answering – even if wrong § iClicker App for smartphone is not acceptable 8/22/22 Overview, Types & Expressions 12
- 13. What Do I Need for this Class? • Laptop Computer § Capable of running Python (no ChromeBooks!) § Minimum of 8Gb of RAM • Python Installation § Will be using the latest Anaconda version § See instructions on website for how to install • iClicker. Acquire by next Tuesday § Credit for answering – even if wrong § iClicker App for smartphone is not acceptable 8/22/22 Overview, Types & Expressions 13 You can use computers in Phillips 318 if needed.
- 14. What Do I Need for this Class? • Laptop Computer § Capable of running Python (no ChromeBooks!) § Minimum of 8Gb of RAM • Python Installation § Will be using the latest Anaconda version § See instructions on website for how to install • iClicker. Acquire by next Tuesday § Credit for answering – even if wrong § iClicker App for smartphone is not acceptable 8/22/22 Overview, Types & Expressions 14 The only MUST purchase
- 15. This Course is OS Agnostic 8/22/22 Overview, Types & Expressions 15 Windows 10 macOS Catalina macOS 10.15 or higher
- 16. Do NOT Even THINK It! 8/22/22 Overview, Types & Expressions 16 Coming this October
- 17. Do NOT Even THINK It! 8/22/22 Overview, Types & Expressions 17 Coming this October
- 18. Things to Do Before Next Class • Visit the course website: § www.cs.cornell.edu/courses/cs1110/2022fa/ § This IS the course syllabus, updated regularly • Read Get Started § Enroll in Ed Discussions § Register your iClicker online § Sign into CMS and complete Survey 0 § Install Python and complete Lab 0 § Take the academic integrity quiz 8/22/22 Overview, Types & Expressions 18
- 19. Things to Do Before Next Class • Visit the course website: § www.cs.cornell.edu/courses/cs1110/2022fa/ § This IS the course syllabus, updated regularly • Read Get Started § Enroll in Ed Discussions § Register your iClicker online § Sign into CMS and complete Survey 0 § Install Python and complete Lab 0 § Take the academic integrity quiz 8/22/22 Overview, Types & Expressions 19 Will talk about this more next class
- 20. Some Words About About Grades • This class is not curved (in traditional sense) § Curve = competition with other students § This is about material, not your classmates • The grades mean something § A: mastered material; can be a consultant § B: good at material; ready to take 2110 § C: it is a bad idea to take 2110 § D: where did you go? § F: were you ever here? 8/22/22 Overview, Types & Expressions 20
- 21. Some Words About About Grades • But this is not a weed-out course § We know students have different backgrounds § Students can do well regardless of experience • But you may have to work hard! § If no experience, budget 10-12 hours of homework a week 8/22/22 Overview, Types & Expressions 21 A B C D/F All Students 40% 40% 18% 2% Some Experience 37% 41% 20% 2% No Experience 32% 42% 24% 2% 42% 28%
- 22. Some Words About About Grades • But this is not a weed-out course § We know students have different backgrounds § Students can do well regardless of experience • But you may have to work hard! § If no experience, budget 10-12 hours of homework a week 8/22/22 Overview, Types & Expressions 22 A B C D/F All Students 40% 40% 18% 2% Some Experience 37% 41% 20% 2% No Experience 32% 42% 24% 2% Freshmen, No Exp 37% 39% 24% 0% 42% 28%
- 23. Getting Started with Python • Will use the “command line” § OS X/Linux: Terminal § Windows: PowerShell § Purpose of the first lab • Once installed type “python” § Starts an interactive shell § Type commands at >>> § Responds to commands • Use it like a calculator § Use to evaluate expressions 8/22/22 Overview, Types & Expressions 23 This class uses Python 3.9
- 24. The Basics 8/22/22 Overview, Types & Expressions 24 12.345 42 “Hello!” integer Values Types Expressions float (real number) string (of characters) 34 * (23 + 14) "Hel" + "lo!" 1.0 / 3.0
- 25. Expressions and Values 8/22/22 Overview, Types & Expressions 25 • An expression represents something § Python evaluates it, turning it into a value § Similar to what a calculator does • Examples: >>> 2.2 2.2 >>> (3 * 7 + 1) * 0.1 2.2 Value Expression Value Expression (Literal) (Complex)
- 26. • Think about + in Python: >>> 1+2 3 >>> "Hello"+"World" "HelloWorld" • Why does + given different answers? § + is different on data of different types § This idea is fundamental to programming What Are Types? 8/22/22 Overview, Types & Expressions 26 adds numerically glues together
- 27. A type is both •a set of values, and •the operations on them What Are Types? 8/22/22 Overview, Types & Expressions 27
- 28. Example: int • Values: integers § …, –1, 0, 1, … § Literals are just digits: 1, 45, 43028030 § No commas or periods • Operations: math! § +, – (add, subtract) § *, // (mult, divide) § ** (power-of) 8/22/22 Overview, Types & Expressions 28
- 29. Example: int • Values: integers § …, –1, 0, 1, … § Literals are just digits: 1, 45, 43028030 § No commas or periods • Operations: math! § +, – (add, subtract) § *, // (mult, divide) § ** (power-of) • Important Rule: § int ops make ints § (if making numbers) • What about division? § 1 // 2 rounds to 0 § / is not an int op • Companion op: % § Gives the remainder § 7 % 3 evaluates to 1 8/22/22 Overview, Types & Expressions 29
- 30. Example: float • Values: real numbers § 2.51, -0.56, 3.14159 § Must have decimal § 2 is int, 2.0 is float • Operations: math! § +, – (add, subtract) § *, / (mult, divide) § ** (power-of) • Ops similar to int • Division is different § Notice /, not // § 1.0/2.0 evals to 0.5 • But includes //, % § 5.4//2.2 evals to 2.0 § 5.4 % 2.2 evals to 1.0 • Superset of int? 8/22/22 Overview, Types & Expressions 30
- 31. float values Have Finite Precision • Try this example: >>> 0.1+0.2 0.30000000000000004 • The problem is representation error § Not all fractions can be represented as (finite) decimals § Example: calculators represent 2/3 as 0.666667 • Python does not use decimals § It uses IEEE 754 standard (beyond scope of course) § Not all decimals can be represented in this standard § So Python picks something close enough 8/22/22 Overview, Types & Expressions 31
- 32. float values Have Finite Precision • Try this example: >>> 0.1+0.2 0.30000000000000004 • The problem is representation error § Not all fractions can be represented as (finite) decimals § Example: calculators represent 2/3 as 0.666667 • Python does not use decimals § It uses IEEE 754 standard (beyond scope of course) § Not all decimals can be represented in this standard § So Python picks something close enough Expressions vs Values 8/22/22 Overview, Types & Expressions 32
- 33. int versus float • This is why Python has two number types § int is limited, but the answers are always exact § float is flexible, but answers are approximate • Errors in float expressions can propagate § Each operation adds more and more error § Small enough not to matter day-to-day § But important in scientific or graphics apps (high precision is necessary) § Must think in terms of significant digits 8/22/22 Overview, Types & Expressions 33
- 34. Using Big float Numbers • Exponent notation is useful for large (or small) values § –22.51e6 is –22.51 * 106 or –22510000 § 22.51e–6 is 22.51 * 10–6 or 0.00002251 • Python prefers this in some cases >>> 0.00000000001 1e-11 A second kind of float literal Remember: values look like literals 8/22/22 Overview, Types & Expressions 34
- 35. Example: bool • Values: True, False § That is it. § Must be capitalized! • Three Operations § b and c (True if both True) § b or c (True if at least one is) § not b (True if b is not) • Made by comparisons § int, float operations § But produce a bool • Order comparisons: § i < j, i <= j § i >= j, i > j • Equality, inequality: § i == j (not = ) § i != j 8/22/22 Overview, Types & Expressions 35
- 36. Example: str • Values: text, or sequence of characters § String literals must be in quotes § Double quotes: "Hello World!", " abcex3$g<&" § Single quotes: 'Hello World!', ' abcex3$g<&’ • Operation: + (catenation, or concatenation) § 'ab' + 'cd' evaluates to 'abcd’ § concatenation can only apply to strings § 'ab' + 2 produces an error 8/22/22 Overview, Types & Expressions 36