1
00:00:00,880 --> 00:00:03,250
- Before we move ahead to the portion

2
00:00:03,250 --> 00:00:05,800
of this lesson on handling exceptions,

3
00:00:05,800 --> 00:00:08,110
I just wanted to deal with a couple of

4
00:00:08,110 --> 00:00:11,040
remaining open items for file processing.

5
00:00:11,040 --> 00:00:14,456
First of all, we've only
shown you the R and W

6
00:00:14,456 --> 00:00:17,463
file open modes but
there are several other

7
00:00:17,463 --> 00:00:20,220
file open modes these are all of the ones

8
00:00:20,220 --> 00:00:23,520
for text file processing
and each one of these

9
00:00:23,520 --> 00:00:26,690
also has a version with the letter V in it

10
00:00:26,690 --> 00:00:31,323
so R-V, W-V, A-V, R-V+, W-V+, and A-V+

11
00:00:32,670 --> 00:00:35,600
and each of those is for binary files

12
00:00:35,600 --> 00:00:39,080
if in fact you have the
need to process binary files

13
00:00:39,080 --> 00:00:41,980
so you can do reading,
writing and appending and

14
00:00:41,980 --> 00:00:43,880
there's versions of each of those that

15
00:00:43,880 --> 00:00:47,170
allow you to both read and
write in the file as well

16
00:00:47,170 --> 00:00:49,600
so you can pause the video
and take a look at these

17
00:00:49,600 --> 00:00:53,380
descriptions if you'd like to
look at them in more detail.

18
00:00:53,380 --> 00:00:56,170
Now separately, there's a
couple of additional methods

19
00:00:56,170 --> 00:01:00,140
that you may find useful if
you're reading from a file,

20
00:01:00,140 --> 00:01:03,054
there is a read method if it's a text file

21
00:01:03,054 --> 00:01:04,940
it will read characters,

22
00:01:04,940 --> 00:01:07,480
if it's a binary file it will read bytes

23
00:01:07,480 --> 00:01:11,210
and the number of characters
or bytes that you want to read

24
00:01:11,210 --> 00:01:14,750
is specified as an integer
argument to the method

25
00:01:14,750 --> 00:01:17,140
or if you provide no arguments,

26
00:01:17,140 --> 00:01:21,020
it will simply read the
entire contents of the file.

27
00:01:21,020 --> 00:01:24,440
There's also the read line
method which returns one line

28
00:01:24,440 --> 00:01:27,010
of text as a string and that will

29
00:01:27,010 --> 00:01:30,090
include the new line
character if there is one.

30
00:01:30,090 --> 00:01:33,878
This particular method
will return an empty string

31
00:01:33,878 --> 00:01:38,600
if end file is encountered and
if you're writing to a file,

32
00:01:38,600 --> 00:01:42,810
a particularly handy method
is the writelines method.

33
00:01:42,810 --> 00:01:47,730
If you have a sequence of
strings, writelines will output

34
00:01:47,730 --> 00:01:50,520
the entire sequence to the file.

35
00:01:50,520 --> 00:01:52,670
So you may recall when we first began

36
00:01:52,670 --> 00:01:56,100
introducing file processing at
the beginning of this lesson,

37
00:01:56,100 --> 00:01:58,950
we called the write method many times over

38
00:01:58,950 --> 00:02:01,660
to write one record at a time.

39
00:02:01,660 --> 00:02:04,680
Well, if we simply took the
strings that represented

40
00:02:04,680 --> 00:02:08,390
each of those records and threw
them into a list for example

41
00:02:08,390 --> 00:02:11,450
we could have written them
all out in one operation

42
00:02:11,450 --> 00:02:14,860
by passing that list to
the writelines method.

43
00:02:14,860 --> 00:02:19,851
Now, as you may guess, there
are classes that Python uses

44
00:02:19,851 --> 00:02:24,730
to implement the file
objects that we received

45
00:02:24,730 --> 00:02:27,320
back from the open function each time

46
00:02:27,320 --> 00:02:30,490
we opened a file for
reading or for writing.

47
00:02:30,490 --> 00:02:32,496
Those classes are defined in the

48
00:02:32,496 --> 00:02:36,140
Python Standard Library module called I-O

49
00:02:36,140 --> 00:02:38,199
and if you're interested
in looking at the details

50
00:02:38,199 --> 00:02:40,870
of those classes and all
of the different methods

51
00:02:40,870 --> 00:02:44,086
that they provide you can
find that documentation here

52
00:02:44,086 --> 00:02:46,543
on the Python dot org website.