Python core programming, Version 2, 230th, page 9, chapter 9 exercises-answers to Python core programming-self-developed-

The answer in this blog is not from official resources, but from my own exercises, which may be incorrect.

9-1. file filtering. Displays all rows of a file, ignoring the rows starting with. This character is used as annotation symbols for most script files, such as Python, Perl, and Tcl. Additional question: handle comments that do not start with the first character.
[Answer]
(A) The Code is as follows:

fobj = open('c:\Python Test\P_1.txt')for eachLine in fobj:    if eachLine[0] != '#':        print eachLine,fobj.close()

The file p_1.txt is:
Apple
Banana
# Orange
Orange #
Orange # orange
Pie
Donut

[Execution result]
Apple
Banana
Orange #
Orange # orange
Pie
Donut

(B) the additional question code is as follows:

fobj = open('c:\Python Test\P_1.txt')for eachLine in fobj:    switch = True    for i in eachLine[1:]:        if i == '#': switch = False    if switch: print eachLine,fobj.close()

[Execution result]
Apple
Banana
# Orange
Pie
Donut

9-2. File Access. The system prompts you to enter numbers N and file F, and then displays the first N lines of the file.
[Answer]
The Code is as follows:

N = raw_input("Please input the line numbers: ... ")F = raw_input("Please input the full location and file name: ... ")fobj = open(F)k = fobj.readlines()for i in k[:int(N)]:    print i,fobj.close()

[Reference]
Http://www.czug.org/python/pyessentialref/09.htm

9-3. File Information, prompting you to enter a file name, and then display the total number of lines of the text file.
[Answer]
The Code is as follows:

Filename = raw_input ("Please input the file location and name :... ") fobj = open (filename) print len (fobj. readlines () fobj. close () ************ Example 9.1. OS & OS. path Modules Example (ospathex. py) [Example source code] import osfor tmpdir in ('/tmp', r 'C: \ Python test'): if OS. path. isdir (tmpdir): breakelse: print 'no temp directory available 'tmpdir = ''if tmpdir: OS. chdir (tmpdir) cwd = OS. getcwd () print '*** current temporary directory 'print cwd print' *** creating example directory... 'OS. mkdir ('example ') OS. chdir ('example ') cwd = OS. getcwd () print '*** new working directory: 'print cwd print' *** original directory listing: 'print OS. listdir (cwd) print '*** creating test file... 'fobj = open ('test', 'w') fobj. write ('foo \ n') fobj. write ('bar \ n') fobj. close () print '*** updated directory listing: 'print OS. listdir (cwd) print "*** renaming 'test' to 'filetest.txt '" OS. rename ('test', 'filetest.txt ') print' *** updated directory listing: 'print OS. listdir (cwd) path = OS. path. join (cwd, OS. listdir (cwd) [0]) print '*** full file pathname 'print path print' *** (pathname, basename) = 'print OS. path. split (path) print '*** (filename, extension) = 'print OS. path. splitext (OS. path. basename (path) print '*** displaying file contents: 'fobj = open (path) for eachLine in fobj: print eachLine, fobj. close () print '*** deleting test file' OS. remove (path) print '*** updated directory listing: 'print OS. listdir (cwd) OS. chdir (OS. pardir) print '*** deleting test directory' OS. rmdir ('example ') print' *** DONE'

[Execution result]
* ** Current temporary directory
C: \ Python Test
* ** Creating example directory...
* ** New working directory:
C: \ Python Test \ example
* ** Original directory listing:
[]
* ** Creating test file...
* ** Updated directory listing:
['Test']
* ** Renaming 'test' to 'filetest.txt'
* ** Updated directory listing:
Using 'filetest.txt ']
* ** Full file pathname
C: \ Python Test \ example \ filetest.txt
*** (Pathname, basename) =
('C: \ Python Test \ example ', 'filetest.txt ')
*** (Filename, extension) =
('Filetest', '.txt ')
* ** Displaying file contents:
Foo
Bar
* ** Deleting test file
* ** Updated directory listing:
[]
* ** Deleting test directory
* ** DONE