Chapter 9 Answers to exercises in Python core programming (1)

9-1. file filtering. display all lines of a file and ignore the lines starting with the #. This character is used

Comments of Python, Perl, TCL, and many other script files.

#filename:test9-1.pyf=open('F:\\test.txt','r')for eachline in f:    try:        if eachline.lstrip()[0]!='#':             print eachline,    except:        passf.close()

Additional question: handle comments not starting with the first character

#filename:test9-1.py#__doc__f=open('F:\\test.txt','r')for eachline in f:    if '#' in eachline:        r=eachline.find('#')        if r>0 :            #print eachline[r-1:r+2]            if eachline[r-1:r+2]!= r"'#'"  and eachline[r-1:r+2]!=r'"#"':                               print eachline[:r],            else:                print eachline,     else:        print eachline,    f.close()

9-4. File Access. Write a program that displays text files page by page. The system prompts you to enter a file name.
Line 25 of the file, pause and prompt the user to "press any key to continue.", press the key to continue.

Note: End of File Processing

def rbypage():    fname=raw_input("Enter filename:").strip()    fp = open(fname,'r')    while True:        lines=0        for p in range(25):            cline=fp.readline()            if cline!='':                lines+=1                print cline,        if lines<25:            print '\nfile is over'            break        info=raw_input("continue?(Y/N)").upper()        if info=='N':            break    fp.close()rbypage()