Beginnings

Before we can get into some "real" programming we have to learn about some of the basic pieces that make up a program. You will begin with short program, and we will add pieces to that.

Readings from the book The Practice of Computing Using Python.

Chapter 0: The Study of Computer Science
Chapter 1: Beginnings
For those who have not yet purchased a text here is a draft of Chapters 0 and 1.

Videos

  1. Your First Program
    1. First Program (Video)
  2. Program Elements
    1. Types (Video)
    2. Assignment (Video)
    3. Mathematical Expressions (Video)
  3. Working some simple examples
    1. Arithmetic in the Python Shell (Video)
    2. A program to convert money (Video)
  4. Round() behavior
    1. Here are three examples that illustrate how calling the round() function with no second argument, it returns an int. The second argument indicates how many significant digits to the right of a decimal point so a non-zero second argument will return a float. Also, note how it rounds with 0.5.
      2.              In [1]: round(4.5) 
             Out[1]: 4 # returned an int, rounded down
             In [2]: round(4.51)  
             Out[2]: 5 # returned an int, rounded up
             In [3]: round(4.51,1)  
             Out[3]: 4.5 # returned a float, rounded to one decimal place
    2. Python uses "round to nearest, ties to nearest even": When the value you intend to round off is a five, you MUST look at the previous value. If it is even, you round down. If it is odd, you round up. It is called round half to even. For example,
      3.              In [1]: round(26.5) 
             Out[1]: 26 # (6 is even so round down)
             In [2]: round(25.5)  
             Out[2]: 26 # (5 is odd so round up)
    3. Couple more examples:
      4.              In [1]: round(3.5) 
             Out[1]: 4 # returned an int, rounded up
             In [2]: round(4.5)  
             Out[2]: 4 # returned an int, rounded down
             In [3]: round(1.5) 
             Out[3]: 2 # returned an int, rounded up
             In [4]: round(2.5)  
             Out[4]: 2 # returned an int, rounded down
    4. The behavior of round() for floats can be surprising. For example, round(2.675,2) gives 2.67 instead of the expected 2.68. It's a result of the fact that most decimal fractions can't be represented exactly as a float. When the decimal 2.675 is converted to a binary floating-point number, it's again replaced with a binary approximation, whose exact value is: 2.67499999999999982236431605997495353221893310546875 Due to this, it is rounded down to 2.67.

Assignments

  1. Chapter 1 Exercises on Codio
  2. Lab01 (do pre-lab first on D2L)
  3. Project01