Use the XDR format in the script from Exercise 8.21. Solve Exercise 8.21 using XDR as binary format (see page 370). Exercise 8.21 Read/write (x, y) pairs from/to binary files. Write a version of the script datatrans1.py from Chapter 2.2 which works with binary input and output files. Hint: Make two small scripts for generating and viewing binary files with two-column data such that you […]

Reimplement the re.findall function. The findall function in the re module can be used to extract multiple matches. For example, n = re.findall(real, ’3.29 is a number, -4 and 3.28E+00 too’) resuls in n being [’3.29’, ’-4’, ’3.28E+00’] if real is the regular expression for a formatted floating-point number, taken from Chapter 8.2.3. Implement your own findall function using re.search and string manipulation. Hint: Find […]

Make a generator for odd numbers. Write a generator function odds(start) that can be used in a for loop for generating the infinite set of odd numbers starting with start: for i in odds(start=7): if i print i else: break The output here consists of the numbers 7, 9, 11, and so on up to and including 999.

Make a boundary iterator in a 2D grid. The boundary iterator in class Grid2Dit runs through the “interior” points at the right, upper, left, and lower boundaries, always starting at the lower or left point at each of the four parts of the boundary. Add a new boundary iterator that iterates through all boundary points, including the corners, in a counter clockwise sequence. Using the […]

Make a tuple with cyclic indices. Subclass tuple to make a new class cyclictuple (see Chapter 8.6.12) which allows the tuple index to take on any integer value. When an index is out of bounds we just count from the beginning again, thus making the index cyclic. Here is a session: >>> t = cyclictuple((1,2,3)) >>> t[3] 1 >>> t[9] 1 >>> t[10] 2 >>> […]

Copy computer codes into documents. HTML documents that includes segments of program code, think of programming guides as an example, should always contain the most recent version of the program code. This can be achieved by automatically copying the program code into the HTML file prior to distribution of the document. The purpose of this exercise is to develop a script that transforms what we […]

Problematic callbacks to Python from Fortran. In this exercise we shall work with a Scientific Hello World example of the type encountered in Chapter 5.2.1, but now a Fortran routine makes a callback to Python: subroutine hello(hw, r1, r2) external hw real*8 r1, r2, s C compute s=r1+r2 in hw: call hw(r1, r2, s) write(*,*) ’Hello, World! sin(’,r1,’+’,r2,’)=’,s return end Make an extension module tmp […]

Find errors in regular expressions. Consider the following script: #!/usr/bin/env python “””find all numbers in a string””” import re r = r”([+-]?d+.?d*|[+-]?.d+|[+-]?d.d+[Ee][+-]dd?)” c = re.compile(r) s = “an array: (1)=3.9836, (2)=4.3E-09, (3)=8766, (4)=.549” numbers = c.findall(s) # make dictionary a, where a[1]=3.9836 and so on: a = {} for i in range(0,len(numbers)-1,2): a[int(numbers[i])] = float(numbers[i+1]) sorted_keys = a.keys(); sorted_keys.sort() for index in sorted_keys: print “[%d]=%g” […]

Archive all files needed in a LATEX document. LATEX documents often involves a large number of files. Sending a document to others might then be difficult as a style file or figure may easily be missing. The purpose of this exercise is to make a script that interprets the output of running latex on a document and packs all files building up the document in […]

Extend Exercise 5.2 or 5.3 with a callback to Python Modify the solution of Exercise 5.2 or 5.3 such that the function to be integrated is implemented in Python (i.e., perform a callback to Python) and transferred to the C or C++ code as a function argument. The simplest approach is to write the C or C++ wrapper code by hand. Exercise 5.2 Implement a […]