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Exercise problems

Block I

  1. Write a program that identifies every number between two limits that is divisible by 7.
    [ Solution ]
  2. Write a program to convert Celsium ⇔ Fahrenheit. Try different method for passing data to the script:
    • Prompting input on the shell.
    • Accepting arguments passed during script calling.
    • Reading data from a file.
    [ Solution ]
  3. Calculate and print the Fibonacci series: F0 = 1, F1 = 1, Fn = Fn−1 + Fn−2
    [ Solution ]
  4. Write a proram which determines whether a given year is a leap year or not.
    • A year is a leap year, if it divisible by 4 unless
    • it is divisible by 100. In this case it is not a leap year, unless
    • it is divisible by 400.
    [ Solution ]
  5. Define yourself a list containing several elements (different value!). Find an elegant way of deleting a specific element from the list. Tip: index().
    [ Solution ]

Block II

  1. List Comprehensions
    • Many programming language know the concept of stacks. Python has its own equivalent (Queue), but write your own version of a stack. It should emit exeptions, if it’s empty or full.
      [ Solution ]
    • In yesterday’s exercise 4 we determined whether a year was a leap year. Try to accomplish the same task using list comprehensions.
      [ Solution ]
    • When working with large data, e.g. larger than 10000 elements, one should consider a less memory consuming alternative: Generator Expressions. Try to solve the last exercise using generator expressions.
      [ Solution ]
  2. Hamster – Write a script containing a hamster and a board object. The hamster shall move in a pattern and avoid obstacles on the board. Finally the board should have means to display the hamster’s motion.
    [ Solution ] [ Video ]
  3. Polynome – Define a class for polynomials. One shall be able to define, derive, integrate and do math with polynomials. Do not use tools from the module numpy.
    [ Solution ]
  4. Rational numbers – Design a class for rational numbers allowing the four arithmetics. This class shall also be able to return the reduced fraction or a float. Remember:
    • A fraction can be fully reduced by dividing numerator and dominator by the greatest common divisor.
    • Rational numbers are presentated as a fraction p/q, where p ∈ Z and q ∈ N\0.
    [ Solution ]

Block III

  1. Threading– Write a threaded script for retrieving (or generating), processing (e.g. apply a function) and saving values. But do not forget:
    • Instead of starting a thrad for each value, one can assign threads to tasks and pass values to them using queues.
    • Some operations, e.g. I/O, are not "thread-safe". Make sure nothing can go wrong.
    • It can be annoying, if one tries to stop a threaded program, but it continues to run. Make sure the user can abort the program at any point.
    [ Solution]
  2. Calculator – Write a calculator GUI using Tk. The user shall be able to choose a function name (RadioButtons?) and enter a value, which shall be passed to the function, in a separate window (TopLevel?). The shall be closed, if the value is OK, and the result shall be displayed in the initial window.
    [ Solution ]
  3. Write a simple Tic-Tac-Toe game using Tk. But do not forget to save important data, e.g. which field has been hit by which player!
    [ Solution ]
  4. Write a script for managing a phone book. Write a GUI for managing entries and export/import to/from a file or database.
    [ Solution ]
  5. Racetrack – Write a threaded script for simulating a horse race. Horses shall be independently moved forward and the progress shall be displayed in a GUI, where also the winner shall be announced.
    [ Solution ]

Block IV

  • Arrays – Getting used to
    1. Create a 3 × 3-array with arbitrary values not equal 0 and resize it to a 9 × 6 array.
    2. Assign a m × n-slice (m, n != 0, 1, m != n) of the array to a variable.
    3. Set all elements of the slice equal 3/2 pi.
    4. Define an array with length 100 for each property:
      • Distance between elements is logarithmic.
      • The array is empty.
    5. Resize your 9 × 6 array to a 4 × 13 array and to a 1-dim. array.
    6. We have seen select and piecewise. What is the difference between them and where?
    [ Solution ]
  • Matrices
    1. Convert one of your 2-dim. arrays into a matrix.
    2. Create another matrix (same shape) using MatLab syntax.
    3. Perform addition and multiplication with those matrices. Convert matrices to arrays and repeat.
    4. Solve the linear matrix equation:
    [ Solution ]
  • Polynomials
    1. Write a script for determining the roots and extrema – both x- and y- values – of a polynomial. Use e.g. this polynomial:
      f(x) = 1/3*x**5 − 2*x**2 − 6pi*x − 10
      [ Solution ]
    2. Write a script for reading (x, y)-pairs from a file and fitting with a polynomial p. Determine the followin integral:

      Highlight the integration limits using a patch.
      [ Solution ]
    Display your results graphically.
  • Add to your script from exercise 3.2 error bars.
    [ Solution ]
  • Integral and Differential
    1. Write your own functions for integrating and deriving 1-dimensional arrays. Compare your results with the results of the SciPy tools.
    2. Expand your previous script such it can derive 2-dimensional arrays:
    3. [optional] Expand your script to interactively adjust the integration limits.
    [ Solution ]
  • Fourier Transformation
    1. Write a script for expanding fourier series to fit a given function/array.
    2. Expand the script to display a "Fourier spectrum". Remember: A Fourier series looks like this:
    [ Solution ]
    An alternative (more complex, but short) solution involving a time axis and a Fourier transformation.
  • 3D Plotting
    1. Plot 3D Lissajous figures. Optional: Animate them using Mayavi's animate decorator.
    2. Calculate the electrostatic potential due to a series of point charges in three dimensional space and plot equipotential surfaces.
    3. Calculate the time-averaged power distribution of dipoles and quadrupoles. Plot them using contour of volume plots.