1
00:00:00,000 --> 00:00:02,000
Python functions,

2
00:00:02,000 --> 00:00:04,000
these are really important to know.

3
00:00:04,000 --> 00:00:07,800
So most programming languages have this thing called a function,

4
00:00:08,000 --> 00:00:10,910
and we've actually used these a few times, such as 'print',

5
00:00:10,940 --> 00:00:13,260
we've used 'type', we've used 'input',

6
00:00:13,270 --> 00:00:14,910
we've used 'enumerate'.

7
00:00:14,920 --> 00:00:18,610
These are all functions, but these ones all come built-in

8
00:00:18,610 --> 00:00:19,600
with Python.

9
00:00:19,600 --> 00:00:24,000
We can also create our own functions and name them anything we want.

10
00:00:24,000 --> 00:00:27,210
Now, a function is really just a piece of code that takes

11
00:00:27,220 --> 00:00:30,350
a variable and, I don't know, performs some sort of action,

12
00:00:30,380 --> 00:00:33,320
does some sort of logic, and spits out an answer.

13
00:00:33,400 --> 00:00:37,400
So if there was a Python function that was called 'add_two_numbers',

14
00:00:37,400 --> 00:00:41,400
and you put 1 and 45 in there, you would expect

15
00:00:41,400 --> 00:00:44,900
this to then return the number 46.

16
00:00:44,980 --> 00:00:47,860
Well, we're going to learn how to basically create this because

17
00:00:47,870 --> 00:00:51,440
this is not a Python built-in function, but we can create

18
00:00:51,440 --> 00:00:54,000
something like this, and we can make them super complex,

19
00:00:54,000 --> 00:00:55,400
or we can keep them super simple.

20
00:00:55,500 --> 00:00:57,700
But first things first, let's go ahead and take a look at

21
00:00:57,700 --> 00:00:58,900
some of these syntax.

22
00:00:58,900 --> 00:01:01,500
Whenever we create a new function, it always starts with

23
00:01:01,600 --> 00:01:04,700
the three letters 'd-e-f', 'def'.

24
00:01:04,700 --> 00:01:08,800
So we're going to define a new function, and we can call it

25
00:01:08,800 --> 00:01:12,000
'func_name', and we can have parameters in here.

26
00:01:12,040 --> 00:01:14,910
So just as an example, let's keep this simple, and let's not

27
00:01:14,920 --> 00:01:16,080
have any parameters in here.

28
00:01:16,080 --> 00:01:19,700
So we have a function here called 'func_name', and it's supposed to

29
00:01:19,700 --> 00:01:21,900
do something, so 'print("Hello")'.

30
00:01:21,900 --> 00:01:25,300
And now to execute this 'func_name()', we just type 'func_name()',

31
00:01:25,300 --> 00:01:27,300
[no audio]

32
00:01:27,300 --> 00:01:28,400
and it prints out "Hello".

33
00:01:29,200 --> 00:01:33,900
And that's literally all there is to a function, and

34
00:01:33,900 --> 00:01:35,300
we can make this more complex.

35
00:01:35,300 --> 00:01:36,500
We can add more logic in here.

36
00:01:36,580 --> 00:01:39,540
There are some extra caveats like scoping, but we'll talk

37
00:01:39,550 --> 00:01:40,410
about that down the road.

38
00:01:40,600 --> 00:01:45,500
But essentially you just created a function very similar to 'print'.

39
00:01:45,500 --> 00:01:48,400
Now we can create another function, and let's actually create that

40
00:01:48,400 --> 00:01:51,000
'add_two_numbers' function,

41
00:01:51,020 --> 00:01:53,520
and this thing can have a parameter.

42
00:01:53,700 --> 00:01:57,150
So let's say 'num1' is going to be the first parameter,

43
00:01:57,160 --> 00:01:59,730
it's going to be the only parameter right now, and it's going to

44
00:01:59,740 --> 00:02:01,800
'print(answr)', whatever

45
00:02:01,800 --> 00:02:03,300
that's going to be, the 'answer'.

46
00:02:04,100 --> 00:02:06,300
And I'm going to create a variable in here called 'answer',

47
00:02:06,300 --> 00:02:08,100
and that's going to be 'num1 +',

48
00:02:08,120 --> 00:02:09,080
and then just a number

49
00:02:09,080 --> 00:02:12,100
I'm going to tell it to add, so 3.14.

50
00:02:13,500 --> 00:02:16,900
And then we can say 'add_two_numbers',

51
00:02:18,400 --> 00:02:20,000
and then we can put a number in here.

52
00:02:20,030 --> 00:02:23,240
Now this is called an argument or a parameter.

53
00:02:23,720 --> 00:02:26,930
And all we're doing is saying, "Hey, in this particular function,

54
00:02:26,930 --> 00:02:31,300
let's throw in some extra data", and then we can use this

55
00:02:31,300 --> 00:02:33,870
exact variable name inside of this function.

56
00:02:34,500 --> 00:02:37,600
So let's go ahead, and just say 80.

57
00:02:37,640 --> 00:02:40,070
Now this is going to run 'add_two_numbers' together.

58
00:02:40,080 --> 00:02:43,160
This is effectively the number 80, and the 'answer' is going

59
00:02:43,170 --> 00:02:44,780
to be 80 + 3.14,

60
00:02:44,790 --> 00:02:46,730
and it's going to print that 'answer' out to us.

61
00:02:47,210 --> 00:02:52,610
So should this work, this will say 83.14, just like that.

62
00:02:53,400 --> 00:02:56,600
And that is effectively an argument or a parameter.

63
00:02:56,610 --> 00:02:59,540
Now, if we wanted to, we could add two parameters in here.

64
00:02:59,550 --> 00:03:03,020
And I'm going to keep this as the first example, and use a different

65
00:03:03,020 --> 00:03:04,300
cell. 'num1',

66
00:03:04,500 --> 00:03:07,900
and let's go ahead and add a second parameter, 'num2'.

67
00:03:08,500 --> 00:03:11,700
Let's simply say the 'answer = num1 + num2',

68
00:03:11,700 --> 00:03:13,800
and this is actually going to add two numbers together,

69
00:03:13,800 --> 00:03:15,000
two custom numbers.

70
00:03:15,000 --> 00:03:17,000
[no audio]

71
00:03:17,000 --> 00:03:23,400
So 'add_two_numbers'. What numbers do we want to add? Say, 42 and 24

72
00:03:25,100 --> 00:03:26,400
Sure enough, we got 66.

73
00:03:26,400 --> 00:03:27,800
It added our numbers together.

74
00:03:28,800 --> 00:03:33,300
This is great and all, but there's a problem.

75
00:03:33,300 --> 00:03:36,300
We actually can't get 'answer' outside of the function anymore.

76
00:03:36,340 --> 00:03:39,760
So if I type in 'answer', simply does not exist.

77
00:03:39,770 --> 00:03:41,050
This is a scoping problem.

78
00:03:41,060 --> 00:03:44,020
We'll talk about scoping in a future lesson, but essentially

79
00:03:44,020 --> 00:03:46,500
we created a variable here that we don't have access to.

80
00:03:46,500 --> 00:03:51,500
And let's say we wanted to store this number 66 or 83.14

81
00:03:51,500 --> 00:03:54,500
in a new variable, and work with that down the road,

82
00:03:54,520 --> 00:03:57,520
how do we store this in a variable?

83
00:03:58,900 --> 00:04:02,600
Well, up until now, we would simply put it in a variable.

84
00:04:02,660 --> 00:04:06,610
We would say the 'total = add_two_numbers',

85
00:04:06,620 --> 00:04:08,230
and I'll just move that up.

86
00:04:08,230 --> 00:04:11,800
'add_two_numbers', and let's add 12 and 34.

87
00:04:13,400 --> 00:04:18,000
Okay. That printed out the total of 46, but the total value

88
00:04:18,000 --> 00:04:21,399
of this particular variable is not 46.

89
00:04:21,399 --> 00:04:22,399
It's not what you expect.

90
00:04:22,399 --> 00:04:23,800
It's actually nothing right now.

91
00:04:24,000 --> 00:04:26,800
So let's do 'type(total)', and we're going to see this is a

92
00:04:26,800 --> 00:04:28,800
'NoneType' as expected.

93
00:04:28,820 --> 00:04:31,630
So something to keep in mind with a function is,

94
00:04:31,800 --> 00:04:36,600
a function always comes with this idea of returning an 'answer'.

95
00:04:36,600 --> 00:04:40,300
So you give it some data to work with, and it returns an

96
00:04:40,360 --> 00:04:42,660
answer to you, much like a calculator.

97
00:04:42,660 --> 00:04:48,200
So you punch in 90 divided by 3, and at the end it just says 30.

98
00:04:48,270 --> 00:04:53,860
Now, we do that with this keyword 'return', and then we could

99
00:04:53,890 --> 00:04:57,130
return anything we want in here, "anything we want in here".

100
00:04:57,140 --> 00:05:00,220
So let's take an example of this 'return' keyword.

101
00:05:00,220 --> 00:05:01,300
Let's see how this works.

102
00:05:02,200 --> 00:05:04,800
So let's create a new function in here, and let's call it

103
00:05:04,800 --> 00:05:07,600
'get_name', and it's not going to take any parameters,

104
00:05:07,600 --> 00:05:10,400
and all it's going to do is 'return "Kalob"'.

105
00:05:10,960 --> 00:05:14,200
Now, if I do 'get_name()' with the parentheses because it's a

106
00:05:14,210 --> 00:05:18,450
function, okay, it returned 'Kalob' as a string.

107
00:05:18,450 --> 00:05:19,400
So that's good.

108
00:05:19,400 --> 00:05:21,800
But I don't have a variable to work with here.

109
00:05:21,800 --> 00:05:24,600
So if I wanted to store this in a variable, I could say 'name

110
00:05:24,600 --> 00:05:25,900
= get_name',

111
00:05:26,800 --> 00:05:28,700
and then we could 'print(name)'.

112
00:05:29,800 --> 00:05:32,700
We could 'type(name)', which is going to be a string, because

113
00:05:32,760 --> 00:05:34,580
that's what we told it to return

114
00:05:34,590 --> 00:05:36,380
here. Quotations means it's a string.

115
00:05:37,500 --> 00:05:41,000
And now we're able to store function logic in a variable

116
00:05:41,000 --> 00:05:42,500
using the 'return' keyword.

117
00:05:42,520 --> 00:05:47,080
Now, let's go ahead and create a custom greeting function.

118
00:05:47,090 --> 00:05:52,390
So let's do 'def greeting()', and it's going to take a 'name',

119
00:05:52,500 --> 00:05:55,500
and this is simply going to return an f-string.

120
00:05:55,500 --> 00:05:59,300
"Welcome to Python for Everybody",

121
00:05:59,900 --> 00:06:00,900
and then the ''.

122
00:06:00,900 --> 00:06:02,900
[no audio]

123
00:06:02,900 --> 00:06:05,000
And if we run 'greeting' with a 'name' in here,

124
00:06:05,700 --> 00:06:06,700
'Henry'.

125
00:06:08,100 --> 00:06:11,000
Okay, cool. But that's still not in any sort of variable.

126
00:06:11,060 --> 00:06:14,090
So we could now assign this to a variable saying, I don't

127
00:06:14,100 --> 00:06:16,400
know, the 'sentence' or the welcome sentence is going to be

128
00:06:16,500 --> 00:06:22,100
'greeting('henry')', and let's make that capital 'H', because it's a name,

129
00:06:23,800 --> 00:06:25,300
and then we can use this later.

130
00:06:25,300 --> 00:06:27,300
So 'sentence'.

131
00:06:27,300 --> 00:06:28,800
And why is this important?

132
00:06:28,800 --> 00:06:31,400
Because now we can do things like 'sentence.',

133
00:06:31,400 --> 00:06:34,800
we can 'count' the number of times there's an "o" in here.

134
00:06:35,700 --> 00:06:37,500
There's five "o" in the sentence.

135
00:06:37,800 --> 00:06:40,800
We can do things like 'sentence.upper'.

136
00:06:40,800 --> 00:06:44,300
And so effectively we've performed some sort of logic in

137
00:06:44,300 --> 00:06:45,580
this function called 'greeting()'.

138
00:06:45,590 --> 00:06:48,460
And then with the 'return' keyword, we were able to store that

139
00:06:48,460 --> 00:06:52,100
in a variable, and now we can do anything else with that variable.

140
00:06:52,100 --> 00:06:55,100
Now, whenever you see this 'return' keyword, it is a lot like

141
00:06:55,100 --> 00:06:56,700
the 'break' keyword in a loop,

142
00:06:56,760 --> 00:07:00,150
any code below it is not going to execute, and it's going to

143
00:07:00,160 --> 00:07:03,210
immediately exit the function, just like 'break' immediately

144
00:07:03,220 --> 00:07:07,780
exit a for loop or a while loop, really, any sort of loop.

145
00:07:07,800 --> 00:07:13,300
So just as an example in here, let's do 'print("WILL THIS RUN?")'.

146
00:07:13,300 --> 00:07:15,940
Because we've noticed that the 'print' statement up here, they

147
00:07:15,950 --> 00:07:17,760
were they, were working perfectly fine.

148
00:07:17,760 --> 00:07:20,600
As soon as we called 'add_two_numbers', it would

149
00:07:20,600 --> 00:07:22,400
print the 'answer' just like this.

150
00:07:22,440 --> 00:07:28,130
So if we run 'greeting()' here, this should say "Welcome to Python

151
00:07:28,140 --> 00:07:29,690
for Everybody", whatever the 'name' is.

152
00:07:29,700 --> 00:07:31,940
So, "Henry". And ,will this run?

153
00:07:32,500 --> 00:07:33,500
We don't know.

154
00:07:33,500 --> 00:07:36,400
So let's go ahead and run this, and run that, and it does not

155
00:07:36,450 --> 00:07:39,260
run. And that's because effectively, Python says there's

156
00:07:39,270 --> 00:07:42,410
a function in here, and it hits a keyword called 'return', and

157
00:07:42,410 --> 00:07:45,500
it essentially thinks that it simply does not exist.

158
00:07:45,500 --> 00:07:49,900
Python does not care that there's anything below this 'return' keyword.

159
00:07:49,900 --> 00:07:52,200
[no audio]

160
00:07:52,200 --> 00:07:54,400
Now, the reason we want to use functions is because

161
00:07:54,470 --> 00:07:56,740
if we have any sort of logic that we're planning over and over

162
00:07:56,750 --> 00:07:59,410
again, and we wanted to be able to change over time,

163
00:07:59,420 --> 00:08:02,380
and change throughout our entire application, we can change

164
00:08:02,380 --> 00:08:03,600
it in just one spot.

165
00:08:03,660 --> 00:08:08,720
So let's create a function in here called 'can_drink',

166
00:08:08,720 --> 00:08:10,400
and it's going to take an 'age',

167
00:08:10,400 --> 00:08:14,930
and we're simply going to say 'if age >

168
00:08:14,930 --> 00:08:19,500
18: return True

169
00:08:19,700 --> 00:08:23,100
else return False.

170
00:08:23,100 --> 00:08:27,300
Now, where I'm from, if you're 18 or older, you can legally drink alcohol,

171
00:08:27,500 --> 00:08:33,500
and this works for lots of places across the globe, but not every place.

172
00:08:33,500 --> 00:08:39,400
So we could say, 'can_kalob_drink = can_drink()',

173
00:08:39,400 --> 00:08:44,299
and then I'll put my age of 30 in here, and 'can_kalob_drink'

174
00:08:45,100 --> 00:08:46,200
is going to be True.

175
00:08:46,200 --> 00:08:48,799
30 is in fact, greater than 18.

176
00:08:48,809 --> 00:08:51,799
So really all this did was say, "Put 30 in here.

177
00:08:53,000 --> 00:08:54,000
Put 30 in here.

178
00:08:54,080 --> 00:08:56,150
'if 30 > 18'

179
00:08:56,159 --> 00:08:57,140
Yes, of course it is.

180
00:08:57,140 --> 00:08:58,200
So 'return True'.

181
00:08:58,280 --> 00:09:04,850
If this was False, if this was a lower number, this would

182
00:09:04,860 --> 00:09:07,700
not be executed and it would run the 'else' statement, and then

183
00:09:07,710 --> 00:09:09,930
'return False' would be the answer.

184
00:09:09,940 --> 00:09:13,610
So we can actually take an example of this, and let's say,

185
00:09:13,670 --> 00:09:17,840
15, and I can no longer drink.

186
00:09:17,850 --> 00:09:20,330
Now, the reason you might want to do something like this

187
00:09:20,340 --> 00:09:23,490
is because in your application you might want to make it

188
00:09:23,490 --> 00:09:25,900
available to lots of people across the world.

189
00:09:25,900 --> 00:09:29,380
But in the United States, you have to be 21 or older to drink,

190
00:09:29,600 --> 00:09:32,700
and actually this should be '>='.

191
00:09:32,720 --> 00:09:36,830
But in the United States, you need to be 21 or older to drink.

192
00:09:36,840 --> 00:09:41,230
So what happens if we constantly wrote in our application,

193
00:09:41,240 --> 00:09:46,420
'if age >=18', do a thing, and then

194
00:09:46,430 --> 00:09:50,500
somewhere down the line, let's say 300 lines of code later,

195
00:09:50,500 --> 00:09:53,800
we have it again, 'if age >= 18',

196
00:09:55,200 --> 00:09:56,200
do some more stuff.

197
00:09:56,200 --> 00:09:58,200
[no audio]

198
00:09:58,200 --> 00:10:01,400
We could also do somewhere down the line again, maybe even

199
00:10:01,400 --> 00:10:10,100
in a different file, 'if age < 18', "#cannot drink". Right.

200
00:10:10,130 --> 00:10:12,790
So we have all these different use cases where we are using

201
00:10:12,800 --> 00:10:15,070
the same logic over and over and over again.

202
00:10:15,080 --> 00:10:17,380
What we can do instead is put this into a function.

203
00:10:18,600 --> 00:10:26,500
And so we can say 'if can_drink()', and then the user's 'age' is,

204
00:10:26,500 --> 00:10:27,300
I don't know, 30.

205
00:10:27,340 --> 00:10:29,590
And we could do it again here.

206
00:10:29,600 --> 00:10:31,500
So I'm just going to copy this.

207
00:10:31,500 --> 00:10:34,500
[no audio]

208
00:10:34,500 --> 00:10:40,000
And because this one is less than, we can say, 'if not', because

209
00:10:40,000 --> 00:10:42,300
that's going to 'return False', cannot drink.

210
00:10:42,340 --> 00:10:45,870
So now we're actually cleaning up our logic because down

211
00:10:45,870 --> 00:10:48,900
the road you can simply change this to 21,

212
00:10:48,920 --> 00:10:51,610
and now it affects all three of these areas.

213
00:10:51,610 --> 00:10:53,100
You don't have to change

214
00:10:53,100 --> 00:10:57,900
[no audio]

215
00:10:57,900 --> 00:11:02,300
18 to 21, to 21, to 21, you don't have to do that.

216
00:11:02,320 --> 00:11:03,480
You can just change it one spot.

217
00:11:04,800 --> 00:11:06,200
Now that's the power behind a function.

218
00:11:06,500 --> 00:11:09,230
We can even get more clever with this and assign it to a

219
00:11:09,240 --> 00:11:12,240
variable and only ever reference that variable instead of

220
00:11:12,250 --> 00:11:14,460
referencing the function over and over and over again.

221
00:11:14,580 --> 00:11:16,230
But that's a little bit boring.

222
00:11:16,240 --> 00:11:19,470
So let's talk about more parameters, more arguments.

223
00:11:19,480 --> 00:11:21,900
Let's look at a 'default' value.

224
00:11:21,900 --> 00:11:24,900
So 'def greeting()',

225
00:11:24,900 --> 00:11:29,700
and let's say we are asking for a 'name'. 'print("Hello,"', and

226
00:11:29,700 --> 00:11:34,000
then the 'name'. We can run 'greeting('Kalob')',

227
00:11:34,000 --> 00:11:35,100
and it's going to say, "Hello, Kalob".

228
00:11:35,300 --> 00:11:38,500
But what if we didn't actually pass in any argument?

229
00:11:39,900 --> 00:11:44,000
We get an error "greeting() missing 1 required positional argument: 'name'".

230
00:11:44,040 --> 00:11:46,220
So it's saying that this 'name' variable is actually missing.

231
00:11:46,220 --> 00:11:48,500
This parameter, this argument is missing.

232
00:11:48,550 --> 00:11:50,940
What we can do instead, is give it a 'default'.

233
00:11:51,000 --> 00:11:53,800
So the default is going to be "Zephyr" in this case.

234
00:11:54,040 --> 00:11:57,310
So if there is no 'name', it's going to default to "Zephyr".

235
00:11:57,320 --> 00:11:59,980
So let's run this cell, and run that cell, and it says, "Hello

236
00:11:59,990 --> 00:12:03,280
Zephyr", but if I specifically overwrite that by giving it

237
00:12:03,290 --> 00:12:08,100
a specific value in here, I can overwrite the default value.

238
00:12:08,100 --> 00:12:13,100
So 'name' is always going to be "Zephyr" by default unless you tell

239
00:12:13,100 --> 00:12:14,100
it otherwise.

240
00:12:14,900 --> 00:12:18,100
In which case this says, "Hello Henry", because we have overwritten it.

241
00:12:18,800 --> 00:12:22,400
So why or how is this even useful?

242
00:12:22,400 --> 00:12:26,210
Let's go ahead and create a new function in here, and it's

243
00:12:26,220 --> 00:12:27,920
going to be called 'create_person',

244
00:12:27,980 --> 00:12:31,010
and what this is going to do is return a dictionary of data

245
00:12:31,010 --> 00:12:35,600
for us. So we could say it needs a 'name', needs an 'age',

246
00:12:35,600 --> 00:12:37,600
[no audio]

247
00:12:37,600 --> 00:12:39,800
The 'role' might be a 'Student'.

248
00:12:39,800 --> 00:12:42,800
Maybe this is for a learning platform,

249
00:12:42,800 --> 00:12:46,500
and so every 'role' by default is going to be a 'Student'.

250
00:12:46,500 --> 00:12:50,250
And let's also pass in the required number of books that

251
00:12:50,260 --> 00:12:51,510
every student needs to have.

252
00:12:51,510 --> 00:12:53,400
And let's say the required number of books, 'required_books'

253
00:12:53,400 --> 00:12:55,200
is going to be 5 by default.

254
00:12:55,900 --> 00:12:59,900
What we can do here now, is we can create a 'person =

255
00:12:59,900 --> 00:13:04,200
a dictionary, and we can say the 'name' is going to be whatever

256
00:13:04,200 --> 00:13:05,500
this 'name' value is;

257
00:13:07,200 --> 00:13:11,800
the 'age' is going to be whatever that 'age' value is from that 'age' variable;

258
00:13:13,100 --> 00:13:15,800
the 'role' is going to be whatever 'role' is,

259
00:13:15,800 --> 00:13:17,600
and by default, that's always going to be 'Student',

260
00:13:17,600 --> 00:13:21,700
so that's always going to be filled out; and 'required_books'

261
00:13:22,900 --> 00:13:24,900
is going to be whatever 'required_books' is.

262
00:13:24,940 --> 00:13:27,600
Now, these keys in here just happen to be the same name,

263
00:13:27,600 --> 00:13:29,200
they don't have to be the same name.

264
00:13:29,200 --> 00:13:32,600
So we could say 'person_name' just as an example,

265
00:13:32,610 --> 00:13:36,710
and 'total_books = required_books', something like

266
00:13:36,710 --> 00:13:38,800
that. And then we could return this entire dictionary.

267
00:13:38,800 --> 00:13:42,100
[no audio]

268
00:13:42,100 --> 00:13:46,200
So now I can create a 'person' called 'kalob'. 'create_person()'.

269
00:13:46,280 --> 00:13:48,110
My 'name' is going to be 'Kalob',

270
00:13:48,170 --> 00:13:49,550
my 'age' is going to be 30,

271
00:13:49,550 --> 00:13:52,800
my 'role' is going to be, I'm going to overwrite this, 'Teacher',

272
00:13:52,800 --> 00:13:55,200
but I'm going to keep 'required_books = 5'.

273
00:13:55,270 --> 00:13:57,070
So 'total_books' is going to say 5.

274
00:13:57,370 --> 00:14:00,430
And when I print out 'kalob', you can see 'person_name',

275
00:14:00,460 --> 00:14:02,870
that's the key here, matches 'Kalob',

276
00:14:03,100 --> 00:14:05,100
that's here; the 'age' is 30;

277
00:14:05,100 --> 00:14:06,100
the 'role' is 'Teacher'.

278
00:14:06,200 --> 00:14:09,360
We actually overwrote the default value for 'role'.

279
00:14:09,900 --> 00:14:12,630
And fun fact, we use a little named argument here.

280
00:14:12,630 --> 00:14:16,200
So we made sure that it was specifically overwriting 'role'.

281
00:14:16,600 --> 00:14:19,300
And the 'total_books' is 5, which we didn't specify at all.

282
00:14:19,310 --> 00:14:22,120
The 'required_books' was not a parameter that we gave it, but

283
00:14:22,130 --> 00:14:23,740
it still used 5 as a default.

284
00:14:25,100 --> 00:14:26,100
Now how is this useful?

285
00:14:26,100 --> 00:14:30,200
Well, we can now say 'nathan = create_person(

286
00:14:31,100 --> 00:14:33,100
"Nathan", 29,

287
00:14:33,900 --> 00:14:39,300
his 'role' is a 'Student', and the 'required_books' he needs

288
00:14:39,300 --> 00:14:41,400
is actually only 2, so we can overwrite that.

289
00:14:41,400 --> 00:14:44,600
And let's take a look at what 'nathan' has. First 'name' is "Nathan";

290
00:14:44,600 --> 00:14:46,300
'age' is 29; 'role' is a 'Student',

291
00:14:46,300 --> 00:14:48,300
so we actually didn't need that at all;

292
00:14:48,350 --> 00:14:50,910
and the 'required_books' is 2.

293
00:14:50,910 --> 00:14:51,990
So let's rerun this.

294
00:14:52,900 --> 00:14:53,900
And it didn't change.

295
00:14:55,100 --> 00:14:58,100
We got rid of 'role = 'Student', and it still just

296
00:14:58,100 --> 00:14:59,100
became the default.

297
00:15:00,100 --> 00:15:03,400
So a function essentially allows us to write all of our logic

298
00:15:03,470 --> 00:15:08,350
in here just once, and then down the road, we can call it

299
00:15:08,360 --> 00:15:12,150
with one line of code, and it will always create and always

300
00:15:12,150 --> 00:15:17,200
work with these five lines of code here, or six lines of code

301
00:15:17,200 --> 00:15:20,500
rather. Now, what I would like you to do, is create

302
00:15:20,500 --> 00:15:21,700
your own function.

303
00:15:21,700 --> 00:15:25,100
Go ahead and create a function that asks for user's age, cast

304
00:15:25,100 --> 00:15:29,800
that value as an integer, and then make the function say,

305
00:15:29,800 --> 00:15:31,600
"You are X years old".

306
00:15:31,680 --> 00:15:34,470
So as a quick little recap, you're going to want to create

307
00:15:34,500 --> 00:15:36,200
a function with 'def',

308
00:15:36,220 --> 00:15:38,860
then the function name, whatever that 'func_name' is going to

309
00:15:38,860 --> 00:15:41,400
be, it needs to take an 'age'.

310
00:15:42,200 --> 00:15:43,700
So 'x' could be the 'age',

311
00:15:43,700 --> 00:15:44,890
or you could just call it 'age',

312
00:15:45,250 --> 00:15:50,890
and then you need to 'return' or 'print' a string that says, "You

313
00:15:50,900 --> 00:15:54,400
are", and then whatever that '' is, "years old".

314
00:15:55,200 --> 00:15:57,600
Last but not least, what I would like you to do is create

315
00:15:57,650 --> 00:16:03,210
this function and then put it in a '.py' file, in a '.py'

316
00:16:03,220 --> 00:16:05,640
file, and then from your command line I want you to run

317
00:16:05,840 --> 00:16:09,410
'python yourfile.py', whatever your file is going to be called,

318
00:16:09,480 --> 00:16:12,000
and you should end up seeing your sentence in here.

319
00:16:12,000 --> 00:16:13,800
Don't forget, you need, you're going to need to call your

320
00:16:13,800 --> 00:16:16,500
function, so just because you have assigned it does not mean

321
00:16:16,570 --> 00:16:17,910
that it's actually going to run.

322
00:16:17,910 --> 00:16:20,100
You're going to need to do something like this.

323
00:16:20,100 --> 00:16:23,100
[no audio]

324
00:16:23,100 --> 00:16:25,400
So go ahead and give that a shot.