Compsci 06/101, Fall 2010 3.1 Compsci 6/101: Sept 6-10 We've looked at the language Python Names and types: int, float, long, String, file, … Operations: *, +, -, /, %, ** Types and values different from "real life" What is 7/3 in Python? What is "champion"[2:5] What's String+String and String*int and String+int For useful work: organizing code/programs Functions, modules, indentation, naming Compsci 06/101, Fall 2010 3.2 Functions: abstractions over code Naming something gives you power How do you find absolute value? What is length of a string? We can write and call functions Re-use and/or modify Store in module, import and re-use functions Import standard modules and use functions from them Functions can (should?) return a value We've seen len return an int, what about file.read? Other functions return Strings, floats, or other types Compsci 06/101, Fall 2010 3.3 Anatomy of a Python function def name(params): body Define a function, provide a name, provide parameters, provide a function body How to decide on name? Do we need parameters? What does body of function do Functions provide a named abstraction over code Huh? What is math.isinf(..) or math.sqrt(..)? Compsci 06/101, Fall 2010 3.4 Design, Implementation, Testing Designing Python code and functions What do you want the code to do? Other aspects of code, e.g., portability, efficiency, size, … Understand how to solve a problem without computer Implementing design in code Translation of ideas into vocabulary of Python We don't have a large vocabulary, but it will grow! Testing code, functions How do you know when function is right? What confidence can testing provide?Compsci 06/101, Fall 2010 3.5 Nancy Leveson: Software Safety Mathematical and engineering aspects, invented the discipline Air traffic control Microsoft word There will always be another software bug; never trust human life solely on software. huffington post? Therac 25: Radiation machine http://en.wikipedia.org/wiki/Therac-25 http://bit.ly/5qOjoH Software and steam engines Compsci 06/101, Fall 2010 3.6 Writing and testing functions Review of slicing operator for strings What is an index, where does indexing begin? Value of s[a:b] compare s[a:] compare s[:b] Review problems from last set of notes Pounds to …, BMI, Heron's formula Algorithm Problem Test (APT) Role in Compsci 6/101 and other courses Similar to Unit Testing, part of Agile Development Compsci 06/101, Fall 2010 3.7 String functions in Python Strings are objects, some functions 'builtin' Use web, or Python: strip, startswith, find, count, … Strings are immutable: "hello".replace("h","j") Python operators/functions that work with strings We've seen len, what about in? What's going on? Slicing review, modify or create new? Views of strings: what are they? From an abstract point of view, from Pythonic POV? Compsci 06/101, Fall 2010 3.8 Jon Kleinberg 2005 MacArthur Fellow, 2008 Infosys Award, 2008 Discover “20 Best Brains under 40” Networks course and book Duke course 96 Spring 2010 "....Try to keep an open mind about topics and areas going on....It's much easier to make progress on a problem when you are enjoying what you are doing. In addition to finding work that is important, find work that has some personal interest for you....I've benefited from a lot of mentoring throughout my career. I think it's important to pass it on to the next generation and work in a mentoring capacity or a teaching capacity with people entering the field....” ACM Infosys
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