Python 2.5 (r25:51918, Sep 19 2006, 08:49:13) 
[GCC 4.0.1 (Apple Computer, Inc. build 5341)] on darwin
Type "copyright", "credits" or "license()" for more information.

IDLE 1.2      
>>> import sys
>>> sys.path.append("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07")

>>> # intro to file-handling in Python

>>> # when you open a file a Python...
>>> # ...you open it for some purpose (for reading,
>>> #    for writing, for appending, etc.)
>>> # ...and returned is an object you can then use
>>> #    to do the desired reading and/or writing
>>> #    (that is, you use methods of that object to
>>> #    read and write)

>>> # The Python open built-in function expects 2 strings
>>> #    as arguments: a string representing the name of
>>> #    the file to be opened, and
>>> #    a string representing what you want to do to the
>>> #    file (the "processing mode")

>>> # (note that the string representing the name of the
>>> #    of the file to be opened can be platform-specific
>>> #    and absolute or relative;
>>> #    if relative, it will be assumed to be relative
>>> #    to the directory from which the script is RUN...)

>>> #  some example processing modes: 'r' - reading
>>> #                                 'w' - writing
>>> #                                 'a' - appending

>>> # what is "relative" is different from IDLE vs. the
>>> #    python interpreter; I'm using IDLE in lecture,
>>> #    so the following will not work.
>>> # (it *would* work in the python interpreter, IF I had
>>> #    called it from the directory where a file
>>> #    lyrics.txt resides...)

>>> infile = open("lyrics.txt", "r")

Traceback (most recent call last):
  File "<pyshell#28>", line 1, in <module>
    infile = open("lyrics.txt", "r")
IOError: [Errno 2] No such file or directory: 'lyrics.txt'

>>> # for IDLE, then, I need to use the absolute pathname for the
>>> #    file in this case. In Windows, this path would look quite
>>> #    different...
>>> # NOTE: if you try to run these - CHANGE the paths used in the open
>>> #    command to correspond to YOUR files (or call python from the
>>> #    directory where those files are/are to be, and just put the
>>> #    RELATIVE file name...)

>>> infile = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt", 'r')

>>> # what are some file methods? (methods I can use
>>> #    with the object returned by open)
>>> #
>>> # (see more from Section 3.9 of the Python Library
>>> # Reference, linked to from public course web page)
>>> #
>>> # read() - read the entire file into a single string
>>> # read(N) - read the next N bytes from the file
>>> # readline() - read next line (through the end-line
>>> #    marker)
>>> # readlines() - read the entire file into a list of string
>>> #    strings
>>> # (and for <line> in <file> is mentioned in 3.9 as
>>> #    recommended for grabbing a line at a time??)
>>> 
>>> # close() - closing the file when you are done
>>> #   (currently, Python WILL close it when the
>>> #   file object is reclained by its garbage collector --
>>> #   BUT, this is not part of the Python language
>>> #   definition. (i.e., that could change in future)
>>> #   BETTER PRACTICE: close what you open!!!
>>> 
>>> # write(S) - write the string S to the file
>>> # writeline(L) - write all line strings in list L into
>>> #    file
>>> 
>>> # so, we have opened "lyrics.txt" for reading, resulting
>>> #    in the file object infile
>>> 
>>> type(infile)
<type 'file'>

>>> # grab all the lines from lyrics.txt and return them as a single string

>>> content_string = infile.read()

>>> len(content_string)
215

>>> content_string
'Always look on the bright si-ide of life,\n(doo-doo, duh-doo duh-doo duh-doo)\nAlways look on the bright si-ide of life!\n\nSpam de Spam, wonderful Spam!\n\nThe rain in Spain stays mainly in the plain,\nin Spain!\nin Spain!'

>>> infile.close()

>>> infile = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt", "r")

>>> # read the first character/byte

>>> infile.read(1)
'A'

>>> # now let's read the next 3 characters

>>> infile.read(3)
'lwa'

>>> # note that the input methods generally return strings --
>>> #    but, remember, you can always convert digits in a string
>>> #    to the corresponding number...

>>> int('3')
3

>>> float('3.1')
3.1000000000000001

>>> # will this read the rest of the current line? yes:

>>> infile.readline()
'ys look on the bright si-ide of life,\n'

>>> # this reads the next line...

>>> infile.readline()
'(doo-doo, duh-doo duh-doo duh-doo)\n'

>>> # will this read the rest of the lines into a list? yes:

>>> what = infile.readlines()

>>> len(what)
7

>>> what
['Always look on the bright si-ide of life!\n', '\n', 'Spam de Spam, wonderful Spam!\n', '\n', 'The rain in Spain stays mainly in the plain,\n', 'in Spain!\n', 'in Spain!']

>>> for line in what:
	print line

	
Always look on the bright si-ide of life!



Spam de Spam, wonderful Spam!



The rain in Spain stays mainly in the plain,

in Spain!

in Spain!

>>> # (note that the line read with readline, readlines
>>> #    includes the newline character... thus the "excess"
>>> #    of newlines above, since print gave me a newline,
>>> #    too...!)

>>> # if you call readlines and you are at the end of file -
>>> #    you get an empty list.

>>> now_what = infile.readlines()

>>> now_what
[]

>>> infile.close()

>>> infile = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt", "r")

>>> # looping through a file, reading a line at a time, is quite reasonable;
>>> #    this is but one example;

>>> nextline = infile.readline()
>>> while (nextline != ''):
	print nextline,
	nextline = infile.readline()

	
Always look on the bright si-ide of life,
(doo-doo, duh-doo duh-doo duh-doo)
Always look on the bright si-ide of life!

Spam de Spam, wonderful Spam!

The rain in Spain stays mainly in the plain,
in Spain!
in Spain!

>>> infile.close()

>>> ends_file = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/ends_w_newline.txt", 'r')
>>> nextline = ends_file.readline()
>>> while (nextline != ''):
	print nextline
	nextline = ends_file.readline()

	
I

end

with

a 

newline.

>>> # (above: what a difference a comma makes in a print command...!)

>>> ends_file.close()

>>> ends_file = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/ends_w_newline.txt", 'r')

>>> nextline = ends_file.readline()
>>> while (nextline != ''):
	print nextline,
	nextline = ends_file.readline()

	
I
end
with
a 
newline.

>>> ends_file.close()

>>> infile = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt", 'r')

>>> infile.readline()
'Always look on the bright si-ide of life,\n'

>>> infile.readline()
'(doo-doo, duh-doo duh-doo duh-doo)\n'

>>> infile.readline()
'Always look on the bright si-ide of life!\n'

>>> infile.readline()
'\n'

>>> infile.readline()
'Spam de Spam, wonderful Spam!\n'

>>> infile.readline()
'\n'

>>> infile.readline()
'The rain in Spain stays mainly in the plain,\n'

>>> infile.readline()
'in Spain!\n'

>>> infile.readline()
'in Spain!'

>>> infile.readline()
''

>>> # above: note that the last line read from this file doesn't end with 
>>> #    \n --- lyrics.txt doesn't happen to end with a newline character;
>>> # (and if you call readline() past the end of file - you get an empty
>>> #    string...)

>>> ends_file = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/ends_w_newline.txt", 'r')

>>> infile.close()

>>> ends_file.readline()
'I\n'

>>> ends_file.readline()
'end\n'

>>> ends_file.readline()
'with\n'

>>> ends_file.readline()
'a \n'

>>> ends_file.readline()
'newline.\n'

>>> ends_file.readline()
''

>>> # ends_w_newline.txt did happen to end with a newline - so we see
>>> #    \n at the end of its last line

>>> ends_file.close()

>>> # note that playing with show_guts.py (posted along with this) shows that
>>> #    where the script is RUNNING is where it looks for
>>> #    a file - not where the script "lives"
>>> # (show_guts.py now has a comment explaining/reminding you how to
>>> #    run a python script from the UNIX/Linux command-line)

>>> # now: some writing practice

>>> crude_copy = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics_copy.txt", 'w')

>>> input = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt", 'r')

>>> # reading all the lines from input's corresponding file to a list - 
>>> #    writing that list of lines into crude_copy's corresponding file

>>> crude_copy.writelines( input.readlines() )

>>> # now, look at what files you have in the current directory --- 
>>> # cs-server> ls
>>> # ... you'll see a file lyrics_copy.txt!
>>> #
>>> # look at the contents of lyrics_copy.txt and lyrics.txt ---
>>> # cs-server> more lyrics_copy.txt
>>> # cs-server> more lyrics.txt
>>> # ...and they sure look similar!
>>> #
>>> # UNIX/Linux diff command shows differences between two files -
>>> #    shows NOTHING if file contents are identical.
>>> # cs-server> diff lyrics.txt lyrics_copy.txt
>>> # ... shows these files' contents are indeed identical.

>>> crude_copy.close()
>>> input.close()

>>> # more writing practice...

>>> write_some_more = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/stuff.txt", "w")

>>> write_some_more.write("Hello, how are you?")
>>> write_some_more.write("Oh, I am fine.")
>>> write_some_more.close()

>>> # now look at stuff.txt (cs-server> more stuff.txt) ---
>>> #    note that write(S) writes exactly the string you
>>> #    give - no newline unless you put one in...
>>> 
>>> # also note: if you open an EXISTING file for
>>> #    writing - the existing contents are NUKED!

>>> outfile = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/stuff.txt", 'w')

>>> outfile.write("Bonjour\n")
>>> outfile.close()

>>> # now look at stuff.txt --- only Bonjour is there!

>>> # appending lets you add to the end of a file without
>>> #    nuking its current contents

>>> outfile = open("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/stuff.txt", 'a')

>>> outfile.write("Comment allez-vous?\n")
>>> outfile.write("Au revoir\n")
>>> outfile.close()

>>> # now you see Bonjour as well as Comment allez-vous and Au revoir

>>> # non-file bonus: interactive input in Python...
>>> # (slight interlude)

>>> # function raw_input takes a string as argument -
>>> #    the "prompt" to be printed to the screen -
>>> #    and it captures whatever the user types
>>> #    (up to the next Enter/return) and returns
>>> #    it as a string

>>> looky = raw_input("Type something, please: ")
Type something, please: 145

>>> looky
'145'

>>> looky = raw_input("Type something else: ")
Type something else: Hi How are YOU???

>>> looky
'Hi How are YOU???'

>>> # there is also a function called input();
>>> #    input tries to collect what is typed
>>> #    and return it as a number.
>>> # BUT: BEWARE!!!
>>> # in grabbing the input, Python EXECUTES it --
>>> #    a malicious user could type in a PYTHON COMMAND
>>> #    along with a number, and that command would
>>> #    be executed --- might delete a file, or who
>>> #    knows what?!
>>> 
>>> # so: safer to stick with raw_input and just convert
>>> #    the string returned to the desired numeric type...
>>> 
>>> # so: a few examples to close...
>>> # first: pig_it.py, an interactive-input example
>>> #   (posted along with this session)
>>> 
>>> import pig_it
Please type string to pig-latinize: yes, I can do this

Your pig-latinized string is: 
es-yay i-ay an-cay o-day his-tay

Thank you, and please come again.

>>> # lect07.py - contains function pig_latin_file (and is posted
>>> #    along with this session)

>>> import lect07

>>> lect07.pig_latin_file("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt", "/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/piggy_lyrics.txt")

>>> # now look and see what is inside piggy_lyrics.txt!

>>> # lect07.py also contains a function letter_freq_file...

>>> lect07.letter_freq_file("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lyrics.txt")

a -  14  :  XXXXXXXXXXXXXX
b -   2  :  XX
d -  12  :  XXXXXXXXXXXX
e -  10  :  XXXXXXXXXX
f -   5  :  XXXXX
g -   2  :  XX
h -   9  :  XXXXXXXXX
i -  18  :  XXXXXXXXXXXXXXXXXX
k -   2  :  XX
l -   9  :  XXXXXXXXX
m -   4  :  XXXX
n -  13  :  XXXXXXXXXXXXX
o -  19  :  XXXXXXXXXXXXXXXXXXX
p -   7  :  XXXXXXX
r -   4  :  XXXX
s -  12  :  XXXXXXXXXXXX
t -   7  :  XXXXXXX
u -   4  :  XXXX
w -   3  :  XXX
y -   4  :  XXXX

>>> lect07.letter_freq_file("/Users/smtuttle/Humboldt/to-back-up/f06cis180py/180py_lectures/180py_lect07/lect07.py")

a -  17  :  XXXXXXXXXXXXXXXXX
b -   2  :  XX
c -   5  :  XXXXX
d -   9  :  XXXXXXXXX
e -  67  :  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
f -  20  :  XXXXXXXXXXXXXXXXXXXX
g -  11  :  XXXXXXXXXXX
h -  11  :  XXXXXXXXXXX
i -  60  :  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
l -  34  :  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
m -  11  :  XXXXXXXXXXX
n -  55  :  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
o -  21  :  XXXXXXXXXXXXXXXXXXXXX
p -  31  :  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
q -   2  :  XX
r -  23  :  XXXXXXXXXXXXXXXXXXXXXXX
s -  13  :  XXXXXXXXXXXXX
t -  54  :  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
u -  26  :  XXXXXXXXXXXXXXXXXXXXXXXXXX
v -   1  :  X
w -  10  :  XXXXXXXXXX
x -   6  :  XXXXXX
y -   3  :  XXX
z -   1  :  X
>>>