Matrix-vector multiply with NumPy arrays. Define a matrix and a vector, e.g., A = array([[1, 2, 3], [4, 5, 6], [7, 8, 10]]) b = array([-3, -2, -1]) Use the NumPy manual to find a function that computes the standard matrixvector product A times b (i.e., the vector whose i-th component is 2 j=0 A[i,j]*b[j]). Work with slicing and matrix multiplication. Extract the 2 × […]

Add error handling with an associated message box. Consider the src/py/gui/simplecalc.py script from Chapter 6.1.10. If the user supplies an invalid formula, say x^2+sin(x), the program crashes. In this case an error message should pop up in a separate window and inform the user about a syntax error in the formula. Perform the necessary modifications of the script. (Hint: Read Chapter 6.3.15 and run pydoc […]

Interactive dump of snapshot plots in an animation. Modify the src/py/gui/animate.py script such that typing p on the keyboard dumps the current frame in PostScript format to a file with filename frame_t=T.ps, where T is a symbol for the current time value. (You may create a subclass of AnimateBLT with a new version of update.)

Use Matlab for curve plotting in the simviz1.py script. The plots in the simviz1.py script can easily be generated by another plotting program than Gnuplot. For example, you can use Matlab. Some possible Matlab statements for generating a plot on the screen, as well as hardcopies in PostScript and PNG format, are listed next. load sim.dat % read sim.dat into a matrix sim plot(sim(:,1),sim(:,2)) % […]

Program with Pmw.OptionMenu in simvizGUI2.py. Modify the simvizGUI2.py script such that the func entry field is replaced by a pulldown menu with the three legal choices (y, siny, y3). Use Pmw.OptionMenu, and place the widget between the entry fields and the Compute button. Reuse the module from Exercise 8.10 to ensure that the option menu is always up-to-date with the legal func names in the […]

Find old and large files in a directory tree. Write a function that traverses a user-given directory tree and returns a list of all files that are larger than X Mb and that have not been accessed the last Y days, where X and Y are parameters to the function. Include an option in this function that moves the files to a subdirectory trash under […]

Introduce SCXX in Exercise 10.11. Modify the script from Exercise 10.10 to take advantage of the SCXX library for simplified programming with the Python C API. Exercise 10.11 Introduce C++ array objects in Exercise 10.10. Add an option to the script developed in Exercise 10.10 such that NumPy arrays can be wrapped in NumPyArray_Float objects from Chapter 10.3.1 to simplify programming. Exercise 10.10 Almost automatic […]

Become a “nobody” user on a web server. The simviz1.py.cgi (or simviz1w.py.cgi) script from Chapter 7.2 generates a new directory with several new files. The owner of these files is often named www or nobody. Hence, you cannot remove these files from your directory unless this www or nobody user has set the right access permissions, i.e., permissions for anyone to delete files. We did […]

Write a GUI for Exercise 3.14. The purpose of this exercise is to write a clean-up script of the type described in Exercise 3.14 (page 126), but now with a graphical user interface. The GUI should be realized as a class, which we call cleanfilesGUI. The directory tree to be searched is given through a text entry in the GUI. (Note that in a path […]

Implement a numerical integration rule in C. As Exercise 5.1, but implement the numerical integration rule and the function to be integrated in C. Exercise 5.1 Implement a numerical integration rule in F77. Implement the Trapezoidal rule (4.1) from Exercise 4.5 on page 150 in F77 along with a function to integrate and a main program. Verify that the program works (check, e.g., that a […]