1
00:00:00,000 --> 00:00:04,585
[MUSIC]

2
00:00:04,585 --> 00:00:07,646
Welcome back, we've been looking
at the tools Python provides for

3
00:00:07,646 --> 00:00:09,670
making our way around file systems.

4
00:00:09,670 --> 00:00:12,500
We're now able to change the directory
we're working in, create paths for

5
00:00:12,500 --> 00:00:13,910
the directories and files, and

6
00:00:13,910 --> 00:00:17,300
check the stats of a file to see
how big it is and other things.

7
00:00:17,300 --> 00:00:20,250
While all of that's pretty handy,
none of that gets us very far if we can't

8
00:00:20,250 --> 00:00:22,880
do things with the files and
directories that we find.

9
00:00:22,880 --> 00:00:25,620
This stage won't focus too
much on writing to files.

10
00:00:25,620 --> 00:00:28,530
Check the teacher's notes if you want
more information on working with files.

11
00:00:28,530 --> 00:00:31,300
Instead, we're going to look at
Python's tools for creating files and

12
00:00:31,300 --> 00:00:33,540
directories as a step by itself.

13
00:00:33,540 --> 00:00:37,340
While this will include writing to files,
we won't spend a lot of time on that.

14
00:00:37,340 --> 00:00:40,530
Okay, let's go see how we can use Python
to create our files and directory trees.

15
00:00:41,960 --> 00:00:43,560
Before we try to make a file or

16
00:00:43,560 --> 00:00:47,480
directory, we should probably make sure
that it doesn't already exist, right?

17
00:00:47,480 --> 00:00:50,640
The OS dot path module already
has a method for this.

18
00:00:50,640 --> 00:00:54,520
So let's say I wanted to make the
bootstrap directory in this workspace so

19
00:00:54,520 --> 00:00:57,800
I've imported the OS,
I can do OS dot path dot exists.

20
00:00:58,850 --> 00:01:04,290
And I can search for bootstrap, and
I get back true, that it does exist so

21
00:01:04,290 --> 00:01:07,870
great, I know it exists,
I can avoid trying to create it again.

22
00:01:07,870 --> 00:01:15,020
And this works for files as well so
I can do bootstrap/js/npm.js.

23
00:01:15,020 --> 00:01:16,310
And I get back True.

24
00:01:16,310 --> 00:01:20,570
If I search for say,
treehouse.js, I get back False,

25
00:01:20,570 --> 00:01:22,530
because that one does not exist.

26
00:01:22,530 --> 00:01:23,120
So, that's cool.

27
00:01:23,120 --> 00:01:27,560
I can know whether or
not a file or directory exists.

28
00:01:27,560 --> 00:01:30,400
And, I can create any that I'm missing.

29
00:01:30,400 --> 00:01:33,120
For creating files,
I can of course just use open.

30
00:01:34,190 --> 00:01:38,830
And I can say that I'm going to open,
like test_file.txt.

31
00:01:38,830 --> 00:01:42,110
And I can use W,
to truncate it or erase it, and

32
00:01:42,110 --> 00:01:46,310
then start writing to it, or I can use A,
to append to whatever's there.

33
00:01:46,310 --> 00:01:49,325
And then I can just close the file.

34
00:01:49,325 --> 00:01:51,760
File's been opened,
it's been written to, it's been closed.

35
00:01:51,760 --> 00:01:53,980
And that works, but
it takes two steps, and

36
00:01:53,980 --> 00:01:56,150
I have to remember to use either W or A.

37
00:01:56,150 --> 00:02:01,910
If I was to try to do, like say,
test_file2 and I left off the w.

38
00:02:01,910 --> 00:02:04,690
Then Python will complain at me
that that file doesn't exist.

39
00:02:05,930 --> 00:02:13,670
So to avoid doing that,
I would love to use the os.mknod method.

40
00:02:13,670 --> 00:02:16,930
But I can't because I'm
showing this to you on a Mac.

41
00:02:16,930 --> 00:02:20,560
So normally here I would do
bootstrap/js/treehouse.js and

42
00:02:20,560 --> 00:02:23,840
then it would create it.

43
00:02:23,840 --> 00:02:26,925
But if I try and
do this I get back permission denied.

44
00:02:26,925 --> 00:02:31,245
And the reason is because on MacOS and
MacOS only, for

45
00:02:31,245 --> 00:02:37,285
Python to use the os.mknod [SP] function
you have to be running Python as root,

46
00:02:37,285 --> 00:02:40,025
so you would have to have
done like sudo python three.

47
00:02:41,075 --> 00:02:43,145
Now, I don't like that.

48
00:02:43,145 --> 00:02:44,985
I don't like that you have to do that, but

49
00:02:44,985 --> 00:02:47,875
I can't change that because I have
no control over what Apple does.

50
00:02:47,875 --> 00:02:49,685
So if you're watching this course and

51
00:02:49,685 --> 00:02:54,930
you're on a Mac, don't bother with
OS.mknod, you'll have to use the open and

52
00:02:54,930 --> 00:02:58,990
close method, or one of various other
methods that you can find by Googling.

53
00:03:00,090 --> 00:03:05,400
If you're on Linux or Windows,
the OS.mknod will work just fine.

54
00:03:05,400 --> 00:03:06,500
You can create the files.

55
00:03:06,500 --> 00:03:11,840
And by default it will create a file
with the permissions set to 0600.

56
00:03:11,840 --> 00:03:15,020
If you need to know more about modes
you can check the teacher's notes for

57
00:03:15,020 --> 00:03:17,090
our console foundations course.

58
00:03:17,090 --> 00:03:19,820
MKnod can be used to make
more than just files but

59
00:03:19,820 --> 00:03:22,560
that's way beyond
the scope of this course.

60
00:03:22,560 --> 00:03:25,230
As always, check the documentation for
more information and examples.

61
00:03:26,280 --> 00:03:32,330
Okay, so, small rant and
mknod aside, what about directories?

62
00:03:32,330 --> 00:03:35,310
Well, we have two options for
making directories in Python.

63
00:03:35,310 --> 00:03:40,870
If I only want to make one directory
I can do that directly with os.mkdir.

64
00:03:40,870 --> 00:03:44,710
So I could just say,
make the directory templates and

65
00:03:44,710 --> 00:03:47,170
Python will make this directory.

66
00:03:47,170 --> 00:03:50,180
If I look over here, I can see hey,
I have a templates directory and

67
00:03:50,180 --> 00:03:55,550
there's my test file that I created and
didn't do anything with.

68
00:03:55,550 --> 00:03:59,450
Using mkdir though would get very annoying
if you had to make a deep tree of

69
00:03:59,450 --> 00:04:03,380
directories that all had to be
made from the bottom back up.

70
00:04:03,380 --> 00:04:08,730
Or rather, from the top down because you'd
have to do it one directory at a time.

71
00:04:08,730 --> 00:04:12,500
Luckily there is the makedirs function.

72
00:04:12,500 --> 00:04:15,900
And this one will create
them all the way down.

73
00:04:15,900 --> 00:04:18,570
First though,
I wanna delete this templates directory so

74
00:04:18,570 --> 00:04:24,720
I'm gonna delete that, and then I'm gonna
make, templates, layouts, and mobile.

75
00:04:24,720 --> 00:04:27,990
So you can see, I have three directories
there, the templates directory and

76
00:04:27,990 --> 00:04:29,660
inside of that it's gonna be
the layouts directory, and

77
00:04:29,660 --> 00:04:31,610
inside of that will be
the mobile directory.

78
00:04:32,760 --> 00:04:36,450
So now if I come over and I check,
I have templates, I have layouts and

79
00:04:36,450 --> 00:04:37,430
I have mobile.

80
00:04:37,430 --> 00:04:38,270
And on the inside of mobile,

81
00:04:38,270 --> 00:04:41,570
there's nothing because I
haven't put anything there.

82
00:04:41,570 --> 00:04:45,090
Makedirs has an extra argument though
that I think you should know about.

83
00:04:45,090 --> 00:04:48,300
Let's try running the command again,
exactly as we just ran it.

84
00:04:48,300 --> 00:04:53,450
And you can see we get back this new
error which is the FileExistsError.

85
00:04:53,450 --> 00:04:55,400
And it says that this
directory already exists.

86
00:04:55,400 --> 00:04:57,380
It's kind of funny that
it's called FileExists

87
00:04:57,380 --> 00:04:58,730
when it's a directory, but that's fine.

88
00:04:59,860 --> 00:05:00,790
If the target directory,

89
00:05:00,790 --> 00:05:03,440
the one at the end, already exists,
you're gonna get this error.

90
00:05:04,540 --> 00:05:05,970
If that matters to you, great.

91
00:05:05,970 --> 00:05:08,240
Catch the error,
do whatever you need to do there.

92
00:05:08,240 --> 00:05:10,420
Tell the user that the directory
already exists and

93
00:05:10,420 --> 00:05:12,436
you can't make a new one or whatever.

94
00:05:12,436 --> 00:05:16,690
If it doesn't though, if it doesn't
matter to you that the directory exists,

95
00:05:16,690 --> 00:05:20,640
you can tell Python that it's
okay if the directory exists.

96
00:05:20,640 --> 00:05:23,480
So let me clear the screen here and
we'll run this again.

97
00:05:23,480 --> 00:05:29,760
And this time we will say, exist_ok=True
and Python doesn't complain at us.

98
00:05:29,760 --> 00:05:32,600
Python goes you don't care
if the directory exists?

99
00:05:32,600 --> 00:05:34,940
The directory exists,
we're just gonna move on.

100
00:05:34,940 --> 00:05:38,559
I've found that most of the time,
this is the behavior that I actually want.

101
00:05:38,559 --> 00:05:43,350
There are two things on every function
we've used that's handy to know.

102
00:05:43,350 --> 00:05:45,810
First, all of these paths we've
been providing are relative, but

103
00:05:45,810 --> 00:05:47,730
you can provide absolute paths, too.

104
00:05:47,730 --> 00:05:48,745
The functions will still
work the same way.

105
00:05:48,745 --> 00:05:51,053
They'll just go to the absolute
location you provided,

106
00:05:51,053 --> 00:05:54,540
instead of going forward from
the current working directory.

107
00:05:54,540 --> 00:05:58,570
Second, you can create a path-like object,
like you'd get from pathlib, and

108
00:05:58,570 --> 00:06:01,210
provide that instead of
providing a path as a string.

109
00:06:01,210 --> 00:06:04,810
It's often much handier when working with
paths that are generated by your software

110
00:06:04,810 --> 00:06:07,750
or from user input instead of paths that
you're typing directly into your code.