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CSV and Python

Created by Jérôme Schneider


In this exercise you will learn how to write and read csv files in Python. You need Python csv library to write this exercise.

Exercise 1

Create a function generate_csv(a_list) that will create a csv file called results.csv.

Your function will be called with a list of tuples (like in the following examples). The tuples will contains tuples which contains as a first a key and as a second value the value associated with the key. The keys will always be the same. You must show this keys in the first line of your csv. After this line you need to add the values formatted like this :

  • a list or a tuple must be string: "a,b,c"
  • a date must follow the US Standard: "month/day/year"

You don't need to format the other values.

Your csv must use ',' as separator and '"' as quotechar.

With this example :

In [1]: import datetime

In [2]: from <your_solution> import generate_csv

In [3]: meteo = [(('temperature', 42),
   ...:   ('date', datetime.date(2017, 1, 22)),
   ...:   ('locations', ('Berlin', 'Paris')),
   ...:   ('weather', 'sunny')),
   ...:  (('temperature', -42),
   ...:   ('date', datetime.date(2017, 1, 22)),
   ...:   ('locations', ('Marseille', 'Moscow')),
   ...:   ('weather', 'cloudy'))]

In [4]: generate_csv(meteo)

You should have this in your results.csv:


Excerise 2

Create a function parse_csv() that will read and parse a csv file. You need to read a file called students.csv which will contain in the first line the column names and after the values. You need to return a list of dictionaries which will contain the column name as key and the value as value.

Your function need to parse the csv values like this:

  • Birthdate column: you need to parse it to datetime.date object
  • Marks column: you need to parse it as a list of integers
  • other columns: you need a string

Example with the following students.csv file :

Ada,Lovelace,12/10/1815,"4242,1010",The first one
Linus,Torvald,12/28/1969,"42,21",Have a problem with penguin
Theo,De Raadt,05/19/1968,"18,19,20",This guy is just crazy
Dennis,Ritchie,09/09/1941,"20,20,20",Like a boss
Alan,Turing,06/23/1912,"42,42,42",Shouldn't eat apple

You should have the following result:

In [1]: from <your_solution> import parse_csv

In [2]: parse_csv()
[{'Birthdate': datetime.date(1815, 12, 10),
  'Comments': 'The first one',
  'Firstname': 'Ada',
  'Lastname': 'Lovelace',
  'Marks': [4242, 1010]},
 {'Birthdate': datetime.date(1969, 12, 28),
  'Comments': 'Have a problem with penguin',
  'Firstname': 'Linus',
  'Lastname': 'Torvald',
  'Marks': [42, 21]},
 {'Birthdate': datetime.date(1968, 5, 19),
  'Comments': 'This guy is just crazy',
  'Firstname': 'Theo',
  'Lastname': 'De Raadt',
  'Marks': [18, 19, 20]},
 {'Birthdate': datetime.date(1941, 9, 9),
  'Comments': 'Like a boss',
  'Firstname': 'Dennis',
  'Lastname': 'Ritchie',
  'Marks': [20, 20, 20]},
 {'Birthdate': datetime.date(1912, 6, 23),
  'Comments': "Shouldn't eat apple",
  'Firstname': 'Alan',
  'Lastname': 'Turing',
  'Marks': [42, 42, 42]}]

That's all folk!