Actions

Python for beginners

From Algolit

Literary Python for Beginners

    • run python 2.7 – installed by default on all platforms (Ubuntu, Mac, Windows)

$ python

>>>

    • install python idle 2.7 – ways to interact with Python: shell + editor
    • you can also use independent editors, such as Bluefish editor or Sublime text (not FLOSS! Lime is being developed). Note: commenting code in BLuefish: Ctrl-Alt-C


Next pages: Some vocabulary // Loops and Conditions // Create anthology

LETTER * WORD * SENTENCE

  • Introduction to the objects string & list with their different attributes
  • uses the shell or integrated development environment


# USING STRINGS

A string is a chain of characters / text and can contain any type of characters

A string is defined by " "

* write letter using STRING

>>> "a"

* write several letters

>>> "a, b, c, d"

* write combinations

>>> "a" + "b"

>>> 3

>>> "a" + "and" + "b"

>>> "a" + " and " + "b"

>>> "a" + "+ " + 3 + " is a3" ***

>>> 3*3

>>> "a" + "+ " + "3" + " is a3"

>>> 3 * "algolit" + " in wtc25"


    • Exercise: Write 'I write the alphabet 3 times.'

Note: there are always different possible solutions


* write string as variable

    • Avoids having to retype your string each time you use it
    • You can change values at any time of the writing process

>>> letter = "a"

>>> print letter

>>> word = "algolit"

>>> print word

>>> sentence = "I learn to read and write again at wtc25"

>>> print sentence, letter

    • Exercise: print your letter, word, sentence


* add punctuation

>>> print letter + " " + word + " " + sentence + "."

>>> print letter + "! " + word + "? " + sentence + "."

>>> letter = "i"

>>> print letter + "! " + word + "? " + sentence + "."

    • Exercise: change content of one of variables, over and over, see how result changes


* calculate!

    • the length of the string

>>> len(letter) >>> len(word) >>> len(sentence)


    • we can also consider the letter/word/sentence as fields or grids, in which each letter occupies a specific position

Note: computer starts to count from 0

>>> word[0] >>> word[3]

    • Exercise: what is the middle letter of your sentence?


* Slicing and concatenating strings in order to select letters & compose new words

    • find last letter

>>> zin[-1]

    • find last but one letter

>>> word[-2]

    • find first two letters

>>> word[0:2]

or

>>> word[:2]

    • find 3 letters in the middle

>>> word[2:5]

    • find from 3rd letter till end

>>> word[2:]

    • Exercise: If the word is "solidarity" is, what do you read here?

word[:5] + word[3:]

    • Exercise: rewrite the word as 'liquidity', using slicing


* write with capitals

>>> print letter.lower()

>>> print sentence.upper()


* write first word of sentence with capital letter

>>> print sentence.capitalize()


* note the difference

>>> sentence.title()

>>> word.title()


From STRINGS to LISTS

  • LISTS are MUTABLE vs immutable STRINGS

That is the reason you want to change your string into a list:

>>> sentence.split()

and save it as a new variable:

>>> list_words = sentence.split()

* some of the attributes of string can be used for lists

    • Exercise: which previously mentioned attributes function for lists?


* replace a word in a list

>>> list_words[3] = "wtc25"

>>> print list_words


* remove words

>>> list_words[2:3] = []

Note: list_words[2] = [] → this removes your 3rd element and replaces it by an empty sublist ('nested list')

if you know the word, you can also use list_words.remove(word)

* put back words

>>> list_words[2:3] = ["so", "exciting"]


* shorten a list

>>> list_words[-3:]

  • and save the shortened list into a new variable – the old continues to exist

>>> yezzzz = list_words[-3:]


* combine lists, group two in one

>>> text = [list_words, yezzzz]


* call an element of a sublist

>>> word = text[1][2]


* concatenate lists, merge two into one

>>> print(list_words + yezzzz)

>>> poem = list_words + yezzzz


*add words to your list

>>> poem.append("is") >>> print(poem)


* sort your list alphabetically

>>> poem.sort()


* transform your list into a string again

>>> " ".join(poem)

NOTE: the whitespace / try without

>>> " ".join(poem) + "?"

More information on list operators: https://docs.python.org/2/tutorial/datastructures.html

  • empty your list // you have a brand new sheet of paper :-)

>>> poem[:] = []