1
00:00:02,290 --> 00:00:06,940
Hello welcome to this tutorial on packages and modules

2
00:00:10,320 --> 00:00:14,710
left to understand packages and modules using some examples.

3
00:00:16,680 --> 00:00:19,550
Say for example have created a directory in my system.

4
00:00:20,830 --> 00:00:34,000
Called basic math and this directory has four files and each of these files have an extension.

5
00:00:34,120 --> 00:00:46,930
Dot B white indicating these files contain python script or Python code and each of these files is used

6
00:00:46,930 --> 00:00:50,890
to perform a specific task.

7
00:00:51,030 --> 00:01:01,500
So for example the first file addition dot B Y is used to perform additions on some input variables

8
00:01:02,060 --> 00:01:04,420
or input parameters.

9
00:01:04,440 --> 00:01:14,920
Similarly we have the other file subtraction multiplication and area performing different tasks so instead

10
00:01:14,920 --> 00:01:22,620
of having the code the entire code for different tasks in a single file.

11
00:01:22,750 --> 00:01:32,030
We have split the code into small parts and each of these but is called a module

12
00:01:34,770 --> 00:01:44,010
and a module in Python is a file containing Python definitions and statements in a module and defined

13
00:01:44,010 --> 00:01:50,880
functions classes and variables in order to define a module.

14
00:01:51,050 --> 00:01:59,580
We need to simply use a text editor to type some Python code and save it with the dot B Y extension

15
00:02:00,810 --> 00:02:05,330
and any such file is automatically considered a Python module.

16
00:02:06,560 --> 00:02:15,080
And the module name is molded out of a file name by removing the dot B Y suffix.

17
00:02:15,080 --> 00:02:27,790
So the file name here is addition dot B Y and the module name is Ed. So if you remove the extension

18
00:02:27,850 --> 00:02:38,330
part b y it becomes the module name so a module in Python is a file containing Python definitions and

19
00:02:38,330 --> 00:02:49,150
statements and the modules are built separately and more or less independently and any file which has

20
00:02:49,150 --> 00:03:01,470
the extension dot B Y and counters of proper Python code is considered a Python module next we will

21
00:03:01,470 --> 00:03:05,100
talk about packages in the previous tutorials.

22
00:03:05,100 --> 00:03:07,860
We were introduced to Python packages.

23
00:03:08,040 --> 00:03:19,850
We have downloaded packages from the Python packaging index and a python package is a collection of

24
00:03:20,210 --> 00:03:31,490
modules and we can build applications by putting all of these modules together and a package is basically

25
00:03:31,550 --> 00:03:40,740
a directory but Python modules and a file with the name underscored underscored in it underscored underscore

26
00:03:40,950 --> 00:03:42,520
dot be white.

27
00:03:42,530 --> 00:03:50,630
This means that every directory inside of the Python part which contains a file name double underscored

28
00:03:51,560 --> 00:03:52,000
in it.

29
00:03:52,010 --> 00:03:55,940
Dot be y will be treated as a package by Python.

30
00:03:56,060 --> 00:04:04,490
A package is basically a directory but Python modules and a file with the name double underscore in

31
00:04:04,490 --> 00:04:08,570
a dot B white.

32
00:04:08,590 --> 00:04:17,280
This means that every directory inside of the python but which contains a file named w underscored in

33
00:04:17,280 --> 00:04:25,710
it will be treated as a package by Python so basic underscore might.

34
00:04:25,870 --> 00:04:36,150
In our example is a package and here we have modules in this package.

35
00:04:36,310 --> 00:04:39,470
And what does this inert file contain.

36
00:04:40,590 --> 00:04:49,350
This the inert file can be left empty but we generally place the initialization code for that package

37
00:04:49,440 --> 00:04:51,170
in this file.

38
00:04:51,240 --> 00:05:00,150
We will talk about the initialization code in the upcoming topics but for now we must remember that

39
00:05:00,210 --> 00:05:04,890
a directory must contain a file named double underscore in it.

40
00:05:04,890 --> 00:05:08,010
In order for Python to consider it as a package

41
00:05:10,840 --> 00:05:21,130
Python package can have sub packages and modules in order to further organize the files and packages

42
00:05:21,130 --> 00:05:25,920
can contain nested sub packages to arbitrary length.

43
00:05:25,960 --> 00:05:31,110
So in this example here we have two sub packages.

44
00:05:31,390 --> 00:05:39,910
And in order for Python to treat these two folders or directories as sub packages we have placed the

45
00:05:40,510 --> 00:05:45,320
double underscored in it Phi in these sub packages as well.

46
00:05:45,820 --> 00:05:55,480
So Python packages a collection of modules and these modules co-operate or work together in order to

47
00:05:55,510 --> 00:05:58,570
implement a task next.

48
00:05:58,570 --> 00:06:04,740
Python packages can have sub packages to arbitrary depth.

49
00:06:04,850 --> 00:06:11,740
Next a directory must contain the doublet underscored in it file in order for Python to consider it

50
00:06:11,860 --> 00:06:13,270
as a package.

51
00:06:14,160 --> 00:06:18,120
So we have understood what modules and packages are.

52
00:06:18,870 --> 00:06:21,620
Now let's go to the next example.

53
00:06:21,630 --> 00:06:31,890
So here I have defined two files a dot B Y and b dot B Y and in this module B I have declared the variable

54
00:06:32,040 --> 00:06:43,140
Z which is a global variable and then a function can and as you can see we have not put any function

55
00:06:43,140 --> 00:06:45,890
calls to this particular function.

56
00:06:46,500 --> 00:06:56,310
In the module B next I want to access the variables and the functions that are defined in module B from

57
00:06:56,310 --> 00:07:06,840
the module a in the global scope or the global namespace of the module b we have the attribute Z which

58
00:07:06,840 --> 00:07:19,300
is pointing to the object one and then we also have the function can which is pointing to the function

59
00:07:19,390 --> 00:07:29,410
object and these two attributes in the global namespace are accessible from anywhere in the in the file.

60
00:07:29,410 --> 00:07:37,420
B Not coming to the local scope we have two variables that are defined in the local scope and because

61
00:07:37,420 --> 00:07:42,470
they are defined within the function body of the function.

62
00:07:42,470 --> 00:07:48,690
Carl they are only accessible within this particular function.

63
00:07:48,700 --> 00:07:59,650
Now I want to access the variables and functions that are defined in the module B from module 8 and

64
00:07:59,830 --> 00:08:03,190
Python provide the import.

65
00:08:03,190 --> 00:08:10,650
And from statements in order to access the content the content of a module.

66
00:08:11,020 --> 00:08:19,930
So in order to access the content defined in the module B we will have to put an import statement in

67
00:08:19,930 --> 00:08:31,440
Module 8 so we will have the import statement and we are going to import the module be the python import

68
00:08:31,440 --> 00:08:41,430
statement gives the module a access to everything that is defined in the global scope or namespace of

69
00:08:41,760 --> 00:08:42,970
module B.

70
00:08:43,020 --> 00:08:57,690
So then we import module B in the file a dot B why this import statement gives access to the attribute

71
00:08:57,780 --> 00:09:01,500
in the global scope of module B.

72
00:09:01,500 --> 00:09:13,820
Remember we do not have a function call to the function that is defined in module B can so so we have

73
00:09:13,910 --> 00:09:23,120
access to the function call that is defined in the global namespace of module b and this function can

74
00:09:23,120 --> 00:09:36,150
be called from the module e using the dot notation so using the dot notation B dark Cal we can make

75
00:09:36,210 --> 00:09:47,190
a function call parse the arguments when Python encounters an import statement in a file it performs

76
00:09:47,250 --> 00:09:49,150
a sequence of steps.

77
00:09:49,290 --> 00:09:53,790
Now let's see the steps involved when importing a module.