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11_Day_Functions/11_functions.md
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@ -9,10 +9,9 @@
<sub>Author:
<a href="https://www.linkedin.com/in/asabeneh/" target="_blank">Asabeneh Yetayeh</a><br>
<small> First Edition: Nov 22 - Dec 22, 2019</small>
<small> Second Edition: July, 2021</small>
</sub>
</div>
</div>
[<< Day 10](../10_Day_Loops/10_loops.md) | [Day 12 >>](../12_Day_Modules/12_modules.md)
@ -33,20 +32,23 @@
- [Default and Arbitrary Number of Parameters in Functions](#default-and-arbitrary-number-of-parameters-in-functions)
- [Function as a Parameter of Another Function](#function-as-a-parameter-of-another-function)
- [💻 Exercises: Day 11](#-exercises-day-11)
- [Exercises: Level 1](#exercises-level-1)
- [Exercises: Level 2](#exercises-level-2)
- [Exercises: Level 3](#exercises-level-3)
# 📘 Day 11
## Functions
So far we have seen many built-in python functions. In this section, we will focus on custom functions. What is a function? Before we start making functions, lets learn what a function is and why we need them?
So far we have seen many built-in Python functions. In this section, we will focus on custom functions. What is a function? Before we start making functions, let us learn what a function is and why we need them?
### Defining a Function
A function is a reusable block of code or programming statements designed to perform a certain task. To define a function, Python provides the _def_ keyword. The following is the syntax for defining a function. The function block of code is executed only if we call it.
A function is a reusable block of code or programming statements designed to perform a certain task. To define or declare a function, Python provides the _def_ keyword. The following is the syntax for defining a function. The function block of code is executed only if the function is called or invoked.
### Declaring and Calling a Function
When we make a function we call it declaring a function. When we start using the it we call it calling or invoking a function. Function can be declared with or without parameters.
When we make a function, we call it declaring a function. When we start using the it, we call it *calling* or *invoking* a function. Function can be declared with or without parameters.
```py
# syntax
@ -83,7 +85,7 @@ add_two_numbers()
### Function Returning a Value - Part 1
Function can also return values, if a function does not return any, the value of the function is None. Lets rewrite the above functions using return. From now on, we get a value when calling the function, instead of printing it.
Function can also return values, if a function does not have a return statement, the value of the function is None. Let us rewrite the above functions using return. From now on, we get a value from a function when we call the function and print it.
```py
def generate_full_name ():
@ -115,7 +117,7 @@ In a function we can pass different data types(number, string, boolean, list, tu
codes
codes
# Calling function
function_name(parameter)
print(function_name(argument))
```
**Example:**
@ -147,11 +149,11 @@ def sum_of_numbers(n):
for i in range(n+1):
total+=i
print(total)
sum_of_numbers(10) # 55
sum_of_numbers(100) # 5050
print(sum_of_numbers(10)) # 55
print(sum_of_numbers(100)) # 5050
```
- Two Parameter: A function may or may not have a parameter or parameters. A function may have two or more parameters. If our function takes parameters we should call it with arguments. Let's check a function with two parameters:
- Two Parameter: A function may or may not have a parameter or parameters. A function may also have two or more parameters. If our function takes parameters we should call it with arguments. Let us check a function with two parameters:
```py
# syntax
@ -160,7 +162,7 @@ sum_of_numbers(100) # 5050
codes
codes
# Calling function
function_name(arg1, arg2)
print(function_name(arg1, arg2))
```
**Example:**
@ -181,7 +183,7 @@ def calculate_age (current_year, birth_year):
age = current_year - birth_year
return age;
print('Age: ', calculate_age(2019, 1819))
print('Age: ', calculate_age(2021, 1819))
def weight_of_object (mass, gravity):
weight = str(mass * gravity)+ ' N' # the value has to be changed to a string first
@ -200,7 +202,7 @@ def function_name(para1, para2):
codes
codes
# Calling function
function_name(para1='John', para2='Doe') # the order of arguments does not matter here
print(function_name(para1 = 'John', para2 = 'Doe')) # the order of arguments does not matter here
```
**Example:**
@ -210,12 +212,12 @@ def print_fullname(firstname, lastname):
space = ' '
full_name = firstname + space + lastname
print(full_name)
print_fullname(firstname='Asabeneh', lastname='Yetayeh')
print(print_fullname(firstname = 'Asabeneh', lastname = 'Yetayeh'))
def add_two_numbers (num1, num2):
total = num1 + num2
print(total)
add_two_numbers(num2=3, num1=2) # Order does not matter
print(add_two_numbers(num2 = 3, num1 = 2)) # Order does not matter
```
### Function Returning a Value - Part 2
@ -272,7 +274,7 @@ print(is_even(7)) # False
```py
def find_even_numbers(n):
evens = []
for i in range(n+1):
for i in range(n + 1):
if i % 2 == 0:
evens.append(i)
return evens
@ -311,10 +313,10 @@ def generate_full_name (first_name = 'Asabeneh', last_name = 'Yetayeh'):
print(generate_full_name())
print(generate_full_name('David','Smith'))
def calculate_age (birth_year,current_year = 2019):
def calculate_age (birth_year,current_year = 2021):
age = current_year - birth_year
return age;
print('Age: ', calculate_age(1819))
print('Age: ', calculate_age(1821))
def weight_of_object (mass, gravity = 9.81):
weight = str(mass * gravity)+ ' N' # the value has to be changed to string first
@ -345,7 +347,7 @@ def sum_all_nums(*nums):
for num in nums:
total += num # same as total = total + num
return total
print(sum_all_nums(2, 3, 5))
print(sum_all_nums(2, 3, 5)) # 10
```
### Default and Arbitrary Number of Parameters in Functions
@ -355,7 +357,7 @@ def generate_groups (team,*args):
print(team)
for i in args:
print(i)
generate_groups('Team-1','Asabeneh','Brook','David','Eyob')
print(generate_groups('Team-1','Asabeneh','Brook','David','Eyob'))
```
### Function as a Parameter of Another Function
@ -366,17 +368,19 @@ def square_number (n):
return n * n
def do_something(f, x):
return f(x)
print(do_something(square_number, 3))
print(do_something(square_number, 3)) # 27
```
🌕 You achieved quite a lot so far. Keep going! You have just completed day 11 challenges and you are 11 steps a head in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You achieved quite a lot so far. Keep going! You have just completed day 11 challenges and you are 11 steps a head in to your way to greatness. Now do some exercises for your brain and muscles.
## 💻 Exercises: Day 11
### Exercises: Level 1
1. Declare a function _add_two_numbers_. It takes two parameters and it returns a sum.
2. Area of a circle is calculated as follows: area = π x r x r. Write a function that calculates _area_of_circle_.
3. Write a function called add_all_nums which takes arbitrary number of arguments and sums all the arguments. Check if all the list items are number types. If not do give a reasonable feedback.
4. Temperature in °C can be converted to °F using this formula: °F = (°C x 9/5) + 32. Write a function which converts °C to °F, _convert_celcius_to-fahrenheit_.
4. Temperature in °C can be converted to °F using this formula: °F = (°C x 9/5) + 32. Write a function which converts °C to °F, _convert_celsius_to-fahrenheit_.
5. Write a function called check-season, it takes a month parameter and returns the season: Autumn, Winter, Spring or Summer.
6. Write a function called calculate_slope which return the slope of a linear equation
7. Quadratic equation is calculated as follows: ax² + bx + c = 0. Write a function which calculates solution set of a quadratic equation, _solve_quadratic_eqn_.
@ -395,7 +399,7 @@ print(reverse_list1(["A", "B", "C"]))
```py
food_staff = ['Potato', 'Tomato', 'Mango', 'Milk'];
print( add_item(food_staff, 'Meat')) # ['Potato', 'Tomato', 'Mango', 'Milk','Meat'];
print(add_item(food_staff, 'Meat')) # ['Potato', 'Tomato', 'Mango', 'Milk','Meat'];
numbers = [2, 3, 7, 9];
print(add_item(numbers, 5)) [2, 3, 7, 9, 5]
```
@ -409,19 +413,20 @@ numbers = [2, 3, 7, 9];
print(remove_item(numbers, 3)) # [2, 7, 9]
```
13. Declare a function named sum_of_numbers. It takes a number parameter and it adds all the numbers in that range.
13. Declare a function named sum_of_numbers. It takes a number parameter and it adds all the numbers in that range.
```py
print(sum_of_numbers(5)) # 15
print(sum_all_numbers(10)) # 55
print(sum_all_numbers(100)) # 5050
```
14. Declare a function named sum_of_odds. It takes a number parameter and it adds all the odd numbers in that range.
15. Declare a function named sum_of_even. It takes a number parameter and it adds all the even numbers in that - range.
16. Declare a function named evens_and_odds . It takes a positive integer as parameter and it counts number of evens and odds in the number.
14. Declare a function named sum_of_odds. It takes a number parameter and it adds all the odd numbers in that range.
15. Declare a function named sum_of_even. It takes a number parameter and it adds all the even numbers in that - range.
### Exercises: Level 2
1. Declare a function named evens_and_odds . It takes a positive integer as parameter and it counts number of evens and odds in the number.
```py
print(evens_and_odds(100))
@ -429,14 +434,17 @@ print(sum_all_numbers(100)) # 5050
# The number of evens are 51.
```
17. Call your function factorial, it takes a whole number as a parameter and it return a factorial of the number
18. Call your function _is_empty_, it takes a parameter and it checks if it is empty or not
19. Write different functions which take lists. They should calculate_mean, calculate_median, calculate_mode, calculate_range, calculate_variance, calculate_std (standard deviation).
20. Write a function called is_prime, which checks if a number is prime.
21. Write a functions which checks if all items are unique in the list.
22. Write a function which checks if all the items of the list are of the same data type.
23. Write a function which check if provided variable is a valid python variable
24. Go to the data folder and access the countries-data.py file.
1. Call your function factorial, it takes a whole number as a parameter and it return a factorial of the number
1. Call your function _is_empty_, it takes a parameter and it checks if it is empty or not
1. Write different functions which take lists. They should calculate_mean, calculate_median, calculate_mode, calculate_range, calculate_variance, calculate_std (standard deviation).
### Exercises: Level 3
1. Write a function called is_prime, which checks if a number is prime.
1. Write a functions which checks if all items are unique in the list.
1. Write a function which checks if all the items of the list are of the same data type.
1. Write a function which check if provided variable is a valid python variable
1. Go to the data folder and access the countries-data.py file.
- Create a function called the most_spoken_languages in the world. It should return 10 or 20 most spoken languages in the world in descending order
- Create a function called the most_populated_countries. It should return 10 or 20 most populated countries in descending order.