Summary: Today we will help you acquire basic knowledge of the syntax and semantics of Python.
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- Chapter I
1.1. Foreword - Chapter II
2.1. Instructions - Chapter III
3.1. Specific instructions of the day - Chapter IV
4.1. Exercise 00 : Data types - Chapter V
5.1. Exercise 01 : Working with files - Chapter VI
6.1. Exercise 02 : Search by key - Chapter VII
7.1. Exercise 03 : Search by value and by key - Chapter VIII
8.1. Exercise 04 : Dictionaries - Chapter IX
9.1. Exercise 05 : Search by value or by key - Chapter X
10.1. Exercise 06 : Sorting a dictionary - Chapter XI
11.1. Exercise 07 : Sets - Chapter XII
12.1. Exercise 08 : Working with strings as lists - Chapter XIII
13.1. Exercise 09 : Caesar cipher
Python is the most popular programming language for data science. Why is it so good for that kind of task? Python is an interpreted language. That means that you can easily interact with different pieces of code and get fast results. And that is exactly what we need if we want to analyze data from different angles or try different hyperparameters for a machine learning model. Besides this, Python has a lot of libraries that are suitable for scientific tasks, including data science. Add to this a pretty simple syntax and you will get the most popular programming language for data science tasks.
Just for fun, look at these 19 beautiful guiding principles that influenced the design of Python:
- Beautiful is better than ugly.
- Explicit is better than implicit.
- Simple is better than complex.
- Complex is better than complicated.
- Flat is better than nested.
- Sparse is better than dense.
- Readability counts.
- Special cases aren’t special enough to break the rules.
- Although practicality beats purity.
- Errors should never pass silently.
- Unless explicitly silenced.
- In the face of ambiguity, refuse the temptation to guess.
- There should be one - and preferably only one - obvious way to do it.
- Although that way may not be obvious at first unless you’re Dutch.
- Now is better than never.
- Although never is often better than right now.
- If the implementation is hard to explain, it’s a bad idea.
- If the implementation is easy to explain, it may be a good idea.
- Namespaces are one honking great idea - let’s do more of those!
In case you forget any of them, you can just write import this in Python and ythey will quickly appear.
- Use this page as your only reference. Do not listen to any rumors or speculations about how to prepare your solution.
- Here and further on we use Python 3 as the only correct version of Python.
- The python files for python exercises (module01, module02, module03) must have
the following block at the end:
if __name__ == ‘__main__’. - Pay attention to the permissions of your files and directories.
- To be assessed your solution must be in your GIT repository.
- Your solutions will be evaluated by your piscine peers.
- You should not leave any files in your directory other than those explicitly specified by the exercise instructions. It is recommended that you modify your .gitignore to avoid any accidents.
- Your solution must be in your GIT repository for evaluation. Always push only to the develop branch! The master branch will be ignored. Work in the src directory.
- When you need to get precise output in your programs, it is forbidden to display a precalculated output instead of performing the exercise correctly.
- Have a question? Ask your neighbor on the right. If that fails, try your neighbor on the left.
- Your reference material: peers / Internet / Google.
- Remember, you can engage in discussion on the Intra Piscine forum.
- Read the examples carefully. They may require things that are not otherwise specified in the subject.
- And may the Force be with you!
- No code in the global scope. Use functions!
- Each file must ended with a function call in a condition similar to: if name == ’main’: your_function( whatever, parameter, is, required )
- You may place an error handling in this same condition.
- No imports are allowed, except those explicitly mentioned in the section ’Authorized functions’ of the title block of each exercise.
- You can use any built-in function if it is not prohibited in an exercise.
- The exceptions raised by the open() function are not to be handled.
- The interpreter to be used is Python 3
Exercise 00
Data types
Turn-in directory : ex00/
Files to turn in : data_types.py
Allowed functions : any import is restricted
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Like any other language, Python has several built-in data types. In this exercise, you will become familiar with the most popular and useful ones.
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Create a script called data_types.py in which you need to define a data_types() function. In this function, you need to declare 8 variables with different types and print their types on the standard output.
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You must reproduce the following output exactly:
> python3 data_types.py [int, str, float, bool, list, dict, tuple, set] -
It is forbidden to explicitly write the data types in your print. Remember to call your function at the end of your script as explained in the instructions for the day:
if __name__ == '__main__': data_types() -
Put your file in the ex00 folder in the src directory of your repository.
Exercise 01
Working with files
Turn-in directory : ex01/
Files to turn in : read_and_write.py
Allowed functions : any import is restricted
- For this exercise, you are free to define as many functions as you need and to name them whatever you want. In the attached file ds.csv (you will recognize it from the previous day), you will have several columns separated by a comma with different data about vacancies.
- Design a Python script called read_and_write.py whose role is to open the file ds.csv, read the data it contains, replace all the comma delimiters with ’\t’ and save it to another file ds.tsv. Be careful, your data may contain commas. If you replace them, you will corrupt the data.
- Put your script in the ex01 folder in the src directory of your repository.
Exercise 02
Search by key
Turn-in directory : ex02/
Files to turn in : stock_prices.py
Allowed functions : import sys
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You have the following dictionaries to copy to one of your functions:
COMPANIES = { 'Apple': 'AAPL', 'Microsoft': 'MSFT', 'Netflix': 'NFLX', 'Tesla': 'TSLA', 'Nokia': 'NOK' } STOCKS = { 'AAPL': 287.73, 'MSFT': 173.79, 'NFLX': 416.90, 'TSLA': 724.88, 'NOK': 3.37 } -
Write a program that takes a name of a company (ex: Apple) as an argument and displays the stock price (ex: 287.73) on the standard output. If you give the program a company that is not from the dictionary as an argument, your script should display Unknown company. If there are no arguments, or too many arguments, your program should do nothing and quit.
$> python3 stock_prices.py tesla 724.88 $> python3 stock_prices.py Facebook Unknown company $> python3 stock_prices.py Tesla Apple
Exercise 03
Search by value and by key
Turn-in directory : ex03/
Files to turn in : ticker_symbols.py
Allowed functions : import sys
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You have the same two dictionaries from the previous exercise. You should copy them again in one of the functions of your script.
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Create a program this time that takes a ticker symbol (ex: AAPL) and displays the company name and the stock price with space as the delimiter. The rest of the behavior must be identical to that of the previous exercise.
$> python3 ticker_symbols.py tsla Tesla 724.88 $> python3 ticker_symbols.py FB Unknown ticker $> python3 ticker_symbols.py TSLA AAPL
Exercise 04
Dictionaries
Turn-in directory : ex04/
Files to turn in : to_dictionary.py
Allowed functions : any import is restricted
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Create a script named to_dictionary.py into one of the functions of which you need to copy the following list of the tuples as is:
list_of_tuples = [ ('Russia', '25'), ('France', '132'), ('Germany', '132'), ('Spain', '178'), ('Italy', '162'), ('Portugal', '17'), ('Finland', '3'), ('Hungary', '2'), ('The Netherlands', '28'), ('The USA', '610'), ('The United Kingdom', '95'), ('China', '83'), ('Iran', '76'), ('Turkey', '65'), ('Belgium', '34'), ('Canada', '28'), ('Switzerland', '26'), ('Brazil', '25'), ('Austria', '14'), ('Israel', '12') ] -
Your script should transform this variable into a dictionary where the number is the key and a country is the value. The same key may have several values as you see. The script must display the content of the dictionary on standard output accordingly to this precise formatting:
'132' : 'France' '132' : 'Germany' '178' : 'Spain' ... -
Think about why the order is not necessarily identical to that of the example.
Exercise 05
Search by value or by key
Turn-in directory : ex05/
Files to turn in : all_stocks.py
Allowed functions : import sys
- You still have those two dictionaries from ex02. And you should still copy them into one of your functions in the script.
- Write a program that has the following behavior:
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the program must take as an argument a string containing many expressions (to find whatever you want) separated by a comma
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for each expression of the string, the program must detect whether it is a company name or a ticker symbol, or neither
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the program should not be case-sensitive but be able to work with white spaces
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if there are no arguments or too many arguments, the program displays nothing
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when there are two commas in a row in the string, the program does not display anything
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the program must display the results separated by a line break and use the following formatting:
$ python3 all_stocks.py 'TSLA , aPPle, Facebook' TSLA is a ticker symbol for Tesla Apple stock price is 287.73 Facebook is an unknown company or an unknown ticker symbol $ python3 all_stocks.py 'TSLA,, apple' $ python3 all_stocks.py 'TSLA, , apple' $ python3 all_stocks.py TSLA AAPL
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Exercise 06
Sorting a dictionary
Turn-in directory : ex06/
Files to turn in : dict_sorter.py
Allowed functions : any import is restricted
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In this exercise, you need to take the list of tuples from ex04 with the countries and numbers and make a dictionary out of it where the countries are keys and the numbers are values . You should copy it into one of your functions in the script.
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Write a program that displays the country names in descending order by number, then in alphabetical order by name if the numbers are equal. You need to display one per line, without the numbers:
The USA Spain Italy France Germany ...
Exercise 07
Sets
Turn-in directory : ex07/
Files to turn in : marketing.py
Allowed functions : import sys
In this exercise, imagine that you work in a marketing department. You will operate with different lists of email accounts. The first list is your clients’ email accounts. The second list contains the email accounts of the participants in your most recent event (some of them were your clients). The third list contains the accounts of your clients who viewed your most recent promotional email.
In business terms, you need to:
- Create a list of those clients who have not seen your promotional email yet. The list will be sent to the call center to reach those people.
- Create a list of the participants who are not your clients. You will send them an introductory email about your products.
- Create a list of the clients who did not participate in the event. You will send them a link to the video and slides of the event.
Technical details:
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Create different functions that convert your lists to sets and use the set operators that you need to use to perform the aforementioned business tasks and return the required lists of email accounts.
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Arrange your code in a script. The script takes the name of the task to perform as an argument: call_center, potential_clients, loyalty_program. If the wrong name is given, raise an exception.
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For this exercise you need to use the following three lists:
clients = ['andrew@gmail.com', 'jessica@gmail.com', 'ted@mosby.com', 'john@snow.is', 'bill_gates@live.com', 'mark@facebook.com', 'elon@paypal.com', 'jessica@gmail.com'] participants = ['walter@heisenberg.com', 'vasily@mail.ru', 'pinkman@yo.org', 'jessica@gmail.com', 'elon@paypal.com', 'pinkman@yo.org', 'mr@robot.gov', 'eleven@yahoo.com'] recipients = ['andrew@gmail.com', 'jessica@gmail.com', 'john@snow.is']
Exercise 08
Working with strings as lists
Turn-in directory : ex08/
Files to turn in : names_extractor.py, letter_starter.py
Allowed functions : import sys
- Imagine that you work in a corporation where the email accounts always have the same template: name.surname@corp.com.
- Create a script that takes the path to a file with such email accounts as an argument. All the emails are delimited by ’\n’ in the file. The script should return a table with the fields: Name, Surname, E-mail delimited by ’\t’. Name and surname values should start from a capital letter. The table should be stored in the file employees.tsv.
- The example:
- Create another script that takes an email, searches the corresponding name from the file created by the first script and returns the first paragraph of a letter:
- Dear Ivan, welcome to our team. We are sure that it will be a pleasure to work with you. That’s a precondition for the professionals that our company hires.
- It is prohibited to use the structure ’la-la {0}’.format(text). Please, use f-strings. They are faster and more readable.
Exercise 09
Caesar cipher
Turn-in directory : ex09/
Files to turn in : caesar.py
Allowed functions : import sys
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There is something called Caesar cipher that helps encode some text using a shift in the alphabetical order. For example, the encoded version of hello might be tqxxa if we use a shift equal to 12
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Write a program that will encode any string using a given shift or will decode any string using a given shift accordingly to the argument given:
$ python3 caesar.py encode 'ssh -i private.key user@school21.ru' 12 eet -u bduhmfq.wqk geqd@eotaax21.dg $ python3 caesar.py decode 'eet -u bduhmfq.wqk geqd@eotaax21.dg' 12 ssh -i private.key user@school21.ru -
If the scripts are given a string with, for example, Cyrillic symbols, the scripts should raise the exception The script does not support your language yet. If an incorrect number of arguments is given, raise an exception