Day 17

2026-06-03 21:02:42 +08:00 · 2019-12-06 00:42:38 +02:00 · 2019-12-06 00:42:38 +02:00 · 2ceb29f60e
commit 2ceb29f60e
parent 4be616de6d
3 changed files with 299 additions and 10 deletions
--- a/.gitignore
+++ b/.gitignore
@ -4,6 +4,7 @@ readme19-24.md
 readme25-30.md
 playground.py
 res.py
+hello.py
 backup.md
 .DS_Store
 __pycache__
--- a/images/try_except.png
+++ b/images/try_except.png
--- a/readme16-18.md
+++ b/readme16-18.md
@ -12,6 +12,7 @@
 🧳 [Part 10: Day 28 - 30](#) 🔒

 ---
+
 - [📘 Day 16](#%f0%9f%93%98-day-16)
  - [Python Datetime](#python-datetime)
    - [Getting the datetime information](#getting-the-datetime-information)
@ -22,6 +23,19 @@
    - [Difference between two datetime](#difference-between-two-datetime)
    - [Difference between two dates and times using timedelata](#difference-between-two-dates-and-times-using-timedelata)
  - [💻 Exercises: Day 16](#%f0%9f%92%bb-exercises-day-16)
+- [📘 Day 17](#%f0%9f%93%98-day-17)
+  - [Exception Handling](#exception-handling)
+  - [Packing and Unpacking Arguments in Python](#packing-and-unpacking-arguments-in-python)
+    - [Unpacking](#unpacking)
+      - [Unpacking list](#unpacking-list)
+      - [Unpacking dictionary](#unpacking-dictionary)
+    - [Packing](#packing)
+    - [Packing list](#packing-list)
+      - [Packing dictionary](#packing-dictionary)
+  - [Spreading in Python](#spreading-in-python)
+  - [Enumerate](#enumerate)
+  - [Zip](#zip)
+  - [Exercises: Day 17](#exercises-day-17)

 # 📘 Day 16

@ -54,7 +68,9 @@ print(day, month, year, hour, minute)
 print('timestamp', timestamp)
 print(f'{day}/{month}/{year}, {hour}:{minute}')  # 4/12/2019, 23:38
 ```
+
 ### Formating datetime output using strftime
+
 ```py
 from datetime import datetime
 new_year = datetime(2020, 1, 1)
@ -69,7 +85,9 @@ print(day, month, year, hour, minute) #1 1 2020 0 0
 print(f'{day}/{month}/{year}, {hour}:{minute}')  # 1/1/2020, 0:0

 ```
+
 Time formating
+
 ```py
 from datetime import datetime
 # current date and time
@ -83,15 +101,19 @@ time_two = now.strftime("%d/%m/%Y, %H:%M:%S")
 # dd/mm/YY H:M:S format
 print("time two:", time_two)
 ```
+
 ```sh
 time: 01:05:01
 time one: 12/05/2019, 01:05:01
 time two: 05/12/2019, 01:05:01
 ```
-Here are all the *strftime* symbols we use to format time. A reference of all the legal format codes.
+
+Here are all the _strftime_ symbols we use to format time. A reference of all the legal format codes.

 ![strftime](./images/strftime.png)
+
 ### String to time using strptime
+
 ```py
 from datetime import datetime
 date_string = "5 December, 2019"
@ -99,11 +121,14 @@ print("date_string =", date_string)
 date_object = datetime.strptime(date_string, "%d %B, %Y")
 print("date_object =", date_object)
 ```
+
 ```sh
 date_string = 5 December, 2019
 date_object = 2019-12-05 00:00:00
 ```
+
 ### Use date from datetime
+
 ```py
 from datetime import date
 d = date(2020, 1, 1)
@ -115,7 +140,9 @@ print("Current year:", today.year)   # 2019
 print("Current month:", today.month) # 12
 print("Current day:", today.day)     # 5
 ```
+
 ### Time object to represent time
+
 ```py
 from datetime import time
 # time(hour = 0, minute = 0, second = 0)
@ -131,13 +158,15 @@ print("c =", c)
 d = time(10, 30, 50, 200555)
 print("d =", d)
 ```
+
 output  
-a = 00:00:00
-b = 10:30:50
-c = 10:30:50
+a = 00:00:00  
+b = 10:30:50  
+c = 10:30:50  
 d = 10:30:50.200555

 ### Difference between two datetime
+
 ```py
 today = date(year=2019, month=12, day=5)
 new_year = date(year=2020, month=1, day=1)
@ -152,6 +181,7 @@ print('Time left for new year:', diff) # Time left for new year: 26 days, 23: 01
 ```

 ### Difference between two dates and times using timedelata
+
 ```py
 from datetime import timedelta
 t1 = timedelta(weeks=12, days=10, hours=4, seconds=20)
@ -159,23 +189,281 @@ t2 = timedelta(days=7, hours=5, minutes=3, seconds=30)
 t3 = t1 - t2
 print("t3 =", t3)
 ```
+
 ```sh
    date_string = 5 December, 2019
    date_object = 2019-12-05 00:00:00
    t3 = 86 days, 22:56:50
 ```
-## 💻  Exercises: Day 16
+
+## 💻 Exercises: Day 16
+
 1. Get the current day, month, year, hour, minute and timestamp from time date module
 1. Format the current date using in this format: "%m/%d/%Y, %H:%M:%S")
 1. Today is 5 December, 2019. Change this time string to time.
 1. Calculate the time difference from now to new year.
 1. Calculate the time difference between 1 January 1970 and now.
-1. Think about for what you can you use datetime module, 
-    * Time series analysis 
-    * To get time stamp of any activities in an application
-    * And many other users
+1. Think about for what you can you use datetime module,
+   - Time series analysis
+   - To get time stamp of any activities in an application
+   - And many other users

+# 📘 Day 17
+
+## Exception Handling
+
+Python uses _try_ and _except_ to handle error gracefully. A graceful exit (or graceful handling) of error is a simple programming idiom wherein a program detects a serious error condition and "exits gracefully" in a controlled manner as a result. Often the program prints a descriptive error message to a terminal or log as part of the graceful exit, this make our application more robust. The cause of an exception is often external to the program itself. An example of exceptions could be an incorrect input, wrong file name, unable to find a file, a malfunctioning IO device. Graceful handling of errors prevent our application from crashing.
+
+We have cover the different python _error_ types in the previous section. If we use _try_ and _except_ our program don't raise error.
+
+![Try and Except](images/try_except.png)
+
+```py
+try:
+    code in this block if things go well
+except:
+    code in this block run if things go wrong
+```
+
+**Example:**
+
+```py
+try:
+    print(10 + '5')
+except:
+    print('Something goes wrong')
+```
+
+In the above example the second operand is a string. So, we should change to float or int to add it with a number. Therefore, the second block which is the _except_ executed.
+**Example:**
+
+```py
+try:
+    name = input('Enter your name:')
+    year_born = input('Year you born:')
+    age = 2019 - year_born
+
+    print(f'You are {name}. And your age is {age}.')
+except:
+    print('Something goes wrong')
+```
+
+```sh
+Something goes wrong
+```
+
+In the above example, the exception block will run and we do not know exactly the problem. To know the problem we can use the different error types with except.
+
+In the following example, it will handle the error and also tells the kind of error raised.
+
+```py
+except TypeError:
+    print(TypeError)
+except:
+    print('Something goes wrong')
+try:
+    name = input('Enter your name:')
+    year_born = input('Year you born:')
+    age = 2019 - year_born
+    print(f'You are {name}. And your age is {age}.')
+except TypeError:
+    print('Type error occur')
+except ValueError:
+    print('Value error occur')
+except ZeroDivisionError:
+    print('zero division error occur')
+```
+
+```sh
+Enter your name:Asabeneh
+Year you born:1920
+Type error occur
+I alway run.
+```
+
+In the above code the output is going to be _TypeError_.
+
+Now, lets by by adding additional block:
+
+```py
+try:
+    name = input('Enter your name:')
+    year_born = input('Year you born:')
+    age = 2019 - int(year_born)
+
+    print(f'You are {name}. And your age is {age}.')
+except TypeError:
+    print('Type error occur')
+except ValueError:
+    print('Value error occur')
+except ZeroDivisionError:
+    print('zero division error occur')
+
+else:
+    print('I usually run with the try block')
+finally:
+    print('I alway run.')
+```
+
+```sh
+Enter your name:Asabeneh
+Year you born:1920
+You are Asabeneh. And your age is 99.
+I usually run with the try block
+I alway run.
+```
+
+## Packing and Unpacking Arguments in Python
+
+We use two operators:
+
+- \* for tuples
+- \*\* for dictionaries
+
+Let's take as an example below. It takes only arguments but we have list. We can unpack the list and changes to argument.
+
+### Unpacking
+
+#### Unpacking list
+
+```py
+def sum_of_five_nums(a, b, c, d, e):
+    return a + b + c + d + e
+
+lst = [1,2,3,4,5]
+print(sum_of_five_nums(lst)) # TypeError: sum_of_five_nums() missing 4 required positional arguments: 'b', 'c', 'd', and 'e'
+```
+
+When we run the above code, it raises an error because this function takes numbers as arguments not as list. Let's unpack or destructure the list.
+
+```py
+def sum_of_five_nums(a, b, c, d, e):
+    return a + b + c + d + e
+
+lst = [1,2,3,4,5]
+print(sum_of_five_nums(*lst))  # 15
+```
+
+We can also use unpacking in the range builtin function that expects start and end.
+
+```py
+numbers = range(2, 7)  # normal call with separate arguments
+print(list(numbers)) # [2, 3, 4, 5, 6]
+args = [2, 7]
+numbers = range(*args)  # call with arguments unpacked from a list
+print(numbers)      # [2, 3, 4, 5,6]
+
+```
+
+A list or a tuple can be also be unpacked like this:
+
+```py
+countries = ['Finland', 'Sweden', 'Norway', 'Denmark', 'Iceland']
+fin, sw, nor, *rest = countries
+print(fin, sw, nor, rest)   # Finland Sweden Norway ['Denmark', 'Iceland']
+numbers = [1, 2, 3, 4, 5, 6, 7]
+one, *middle,last = numbers
+print(one, middle, last)      #  1 [2, 3, 4, 5, 6] 7
+```
+
+#### Unpacking dictionary
+
+```py
+def unpacking_person_info(name, country, city, age):
+    return f'{name} lives in {country}, {city}. He is {age} year old.'
+dct = {'name':'Asabeneh', 'country':'Finland', 'city':'Helsinki', 'age':250}
+print(unpacking_person_info(**dct)) # Asabeneh lives in Finland, Helsinki. He is 250 years old.
+```
+
+### Packing
+
+Sometimes we never know how many arguments need to be passed to a python function, we can use packing method to allow our function to take unlimited number or arbitrary number of arguments.
+
+### Packing list
+
+```py
+def sum_all(*args):
+    s = 0
+    for i in args:
+        s += i
+    return s
+print(sum_all(1, 2, 3))             # 6
+print(sum_all(1, 2, 3, 4, 5, 6, 7)) # 28
+```
+
+#### Packing dictionary
+
+```py
+def packing_person_info(**kwargs):
+    # check the type of kwargs and it is a dict type
+    # print(type(kwargs))
+	# Printing dictionary items
+    for key in kwargs:
+        print(f"{key} = {kwargs[key]}")
+    return kwargs
+
+print(packing_person_info(name="Asabeneh",
+      country="Finland", city="Helsinki", age=250))
+```
+
+```sh
+name = Asabeneh
+country = Finland
+city = Helsinki
+age = 250
+{'name': 'Asabeneh', 'country': 'Finland', 'city': 'Helsinki', 'age': 250}
+```
+
+## Spreading in Python
+
+Like JavaScript it is possible to spread in python. Lets see the example below:
+
+```py
+lst_one = [1, 2, 3]
+lst_two = [4, 5, 6,7]
+lst = [0, *list_one, *list_two]
+print(lst)          # [0, 1, 2, 3, 4, 5, 6, 7]
+country_lst_one = ['Finland', 'Sweden', 'Norway']
+country_lst_two = ['Denmark', 'Iceland']
+nordic_countries = [*country_lst_one, *country_lst_two]
+print(nordic_countries)        ['Finland', 'Sweden', 'Norway', 'Denmark', 'Iceland']
+```
+## Enumerate
+In we are interested in an index of a list, we use *enumerate*.
+```py
+for index, i in enumerate(countries):
+    print('hi')
+    if i == 'Finland':
+        print(f'The country {i} has been found at index {index}')
+```
+```sh
+The country Finland has been found at index 1.
+```
+## Zip
+Sometimes we like to combine to lists when we loop through. See the example below:
+```py
+fruits = ['banana', 'orange', 'mango', 'lemon']                    
+vegetables = ['Tomato', 'Potato', 'Cabbage','Onion', 'Carrot']
+fruits_and_veges = []
+for f, v in zip(fruits, vegetables):
+    fruits_and_veges.append({'fruit':f, 'veg':v})
+
+print(fruits_and_veges)
+```
+```sh
+[{'fruit': 'banana', 'veg': 'Tomato'}, {'fruit': 'orange', 'veg': 'Potato'}, {'fruit': 'mango', 'veg': 'Cabbage'}, {'fruit': 'lemon', 'veg': 'Onion'}]
+```
+
+## Exercises: Day 17
+1. names = ['Finland', 'Sweden', 'Norway','Denmark','Iceland', 'Estonia','Russia']. Unpack the first five countries and store them in a variable nordic_countries, store Estonia and Russia in es, and ru respectively.
+   

 [<< Part 5 ](https://github.com/Asabeneh/30-Days-Of-Python/blob/master/readme13-15.md) | [Part 7 >>](https://github.com/Asabeneh/30-Days-Of-Python/blob/master/readme19-21.md)

---
+---
+
+```
+
+```
+
+```