THÉORIE ET PRATIQUE

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Chaînes

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Boucle while

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Listes

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Tableaux 2D

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Leçon 4. Lines

Difficulté :

Exercice«Optimisation SEO»

💻 Python

Vous avez obtenu un poste de spécialiste SEO junior dans une agence Internet. Votre première tâche — Aider à optimiser le site web d'un client. On vous a fourni une liste de mots-clés, mais elle est très « sale » : il y a beaucoup de mots parasites (les soi-disant « stop words »), comme les conjonctions, les prépositions et les requêtes générales telles que « acheter » ou « prix » qui ne portent pas la charge sémantique principale pour une page donnée.

Votre tâche — Écrire un programme qui nettoiera la chaîne d'origine de ces mots parasites et formera une nouvelle chaîne à partir des mots-clés « propres » restants, où ils seront listés séparés par une virgule. Cela aidera à les utiliser ensuite pour les méta-balises sur le site.

Cahier des charges :

Le programme doit prendre une seule ligne contenant des mots-clés séparés par des espaces.
À l'intérieur du programme, une liste de mots parasites doit être définie en dur (par exemple : "acheter", "prix", "combien", "coûter", "dans", "avec", "sur").
Le programme doit diviser la ligne d'entrée en mots individuels.
En utilisant une boucle for, le programme doit parcourir tous les mots.
En utilisant une condition if, pour chaque mot, il faut vérifier s'il s'agit d'un mot parasite. La vérification doit être insensible à la casse (c'est-à-dire « Acheter » et « acheter » — c'est le même mot parasite).
Les mots qui ne sont pas des mots parasites doivent être rassemblés dans une liste séparée.
À la fin, le programme doit afficher une seule ligne composée des mots propres reliés par une virgule et un espace (, ). S'il ne reste aucun mot propre, le programme doit afficher une ligne vide.

Format d entrée

une ligne (chaîne de caractères) avec des mots-clés, séparés par des espaces.

Format de sortie

Chaîne de caractères (string) avec des mots-clés filtrés, séparés par une virgule et un espace.

Exemple

Entrée

Acheter un ordinateur portable ASUS Prix à Moscou

Sortie

ordinateur portable, Asus, Moscou

Indice

methods for working with strings in python

Python provides many built-in methods for working with strings. These are powerful tools that make it easy to manipulate text data. All methods are called with a dot after the variable in which the string is stored, according to the variable scheme.method().

It is important to remember that strings in Python are immutable. This means that none of the methods changes the original string. Instead, they return a new string with the changes applied.

Basic methods for working with strings

1. upper() and lower()

Convert all characters of the string to upper or lower case, respectively.

string = "Hello, World!"
print(string.upper()) # Output: HELLO, WORLD!
print(string.lower()) # Output: hello, world!
print(string) # Output: Hello, World! (the original line has not changed)

A useful tip: These methods are indispensable when you need to compare case-insensitive strings. For example, when checking user input.

user_input = "Yes"
if user_input.lower() =="yes":
print("The user agrees.")

2. strip(), lstrip() and rstrip()

Remove whitespace characters (spaces, tabs, line breaks) from the beginning and end of the line. lstrip() deletes only on the left, and rstrip() deletes only on the right.

string = "  Hello, World!  "
print(string.strip()) # Output: Hello, World!
print(string.lstrip()) # Output: Hello, World!  
print(string.rstrip()) # Output: Hello, World!

A useful tip: These are extremely important methods for "cleaning" data obtained from files or from users, who often accidentally leave unnecessary spaces. As an argument, you can pass a string of characters that need to be deleted.

dirty_string = "!!!Hello, World!?! "
print(dirty_string.strip(" !?")) # Output: Hello, World

3. split() and join()

split() splits a string into a list of substrings using the specified separator. join() collects a string from the list items by inserting a separator string between them.

string = "Hello, World!"
words =string.split(", ")
print(words) # Output: ['Hello', 'World!']

# Reverse operation
joined_string = " | ".join(words)
print(joined_string) # Output: Hello | World!

A useful tip: split() is a standard method for parsing (parsing) data presented as a string, for example, CSV files. join() is the most efficient ("pythonic") way to assemble one large string from many small ones. It works much faster than adding strings in a loop using +.

4. find() and replace()

find() searches for the first occurrence of a substring and returns its index (position). If the substring is not found, returns -1. replace() replaces all occurrences of one substring with another.

string = "Hello, World!"
index = string.find("World")
print(index) # Output: 7

new_string = string.replace("World", "Python")
print(new_string) # Output: Hello, Python!

A useful tip: There is an analog of the find() index() method.. It does the same thing, but if the substring is not found, it raises the error ValueError. Use find() if the absence of a substring is a normal situation, and index(), if it should interrupt the execution of the program. The replace() method can also accept a third argument - the number of substitutions to be made.

5. startswith() and endswith()

They check whether the string begins or ends with a specific substring. Returns True or False.

string = "Hello, World!"
print(string.startswith("Hello")) # Output: True
print(string.endswith("World!"))   # Output: True
print(string.startswith("Bye"))    # Output: False

A useful tip: It is very convenient for quick checking of file formats (filename.endswith(".txt")) or link types (url.startswith("https")).

6. isdigit(), isalpha() and isalnum()

They check what the string consists of.

isdigit(): True if all characters are numbers.
isalpha(): True if all characters are letters.
isalnum(): True if all characters are letters or numbers.

string1 = "12345"
string2 = "Hello"
string3 = "Hello123"

print(f"'{string1}' consists of digits? {string1.isdigit()}")   # Output: True
print(f"'{string2}' consists of letters? {string2.isalpha()}")   # Output: True
print(f"'{string3}' consists of letters and numbers? {string3.isalnum()}") # Output: True
print(f"'{string2}' consists of digits? {string2.isdigit()}") # Output: False

A useful tip: These methods are ideal for validating user input before attempting to convert a string to a number or using it further in the program.

A complete guide to methods

Below is a table with a more complete list of string methods for quick reference.

Method	Purpose
`S.find(str, [start],[end])`	Search for a substring in a string. Returns the number of the first occurrence or -1.
`S.rfind(str, [start],[end])`	Search for a substring in a string. Returns the number of the last occurrence or -1.
`S.index(str, [start],[end])`	Search for a substring in a string. Returns the number of the first occurrence or causes a `ValueError`.
`S.rindex(str, [start],[end])`	Search for a substring in a string. Returns the number of the last occurrence or causes a `ValueError`.
`S.replace(template, replacement[, maxcount])`	Replace the template with a replacement. `maxcount` limits the number of substitutions.
`S.split(character)`	Splitting a line by separator.
`S.isdigit()`	Whether the string consists of numbers.
`S.isalpha()`	Whether the string consists of letters.
`S.isalnum()`	Whether the string consists of numbers or letters.
`S.islower()`	Whether the string consists of lowercase characters.
`S.isupper()`	Whether the string consists of uppercase characters.
`S.isspace()`	Whether the string consists of non-displayed characters (space, `\f`, `\n`, `\r`, `\t`, `\v`).
`S.istitle()`	Whether words in a line begin with a capital letter.
`S.upper()`	Converting a string to uppercase.
`S.lower()`	Converting a string to lowercase.
`S.startswith(str)`	Does the string S start with the template `str`.
`S.endswith(str)`	Does line S end with the `str` template.
`S.join(list)`	Assembling a line from a list separated by S.
`ord(character)`	Converts a character to its ASCII/Unicode code.
`chr(number)`	Converts the ASCII/Unicode code to a character.
`S.capitalize()`	Converts the first character of the string to uppercase, and all the others to lowercase.
`S.center(width, [fill])`	Returns a centered string with the `fill` character at the edges (space by default).
`S.count(str, [start],[end])`	Returns the number of disjoint occurrences of a substring.
`S.expandtabs([tabsize])`	Replaces the tab characters `\t` with spaces.
`S.lstrip([chars])`	Deleting specified characters (or spaces) at the beginning of a line.
`S.rstrip([chars])`	Deleting specified characters (or spaces) at the end of a line.
`S.strip([chars])`	Deleting specified characters (or spaces) at the beginning and end of a line.
`S.partition(template)`	Divides a string by the first occurrence of the separator into three parts: before, the separator itself, and after.
`S.rpartition(sep)`	Divides the string by the last occurrence of the separator into three parts: before, the separator itself, and after.
`S.swapcase()`	Converts lowercase characters to uppercase, and uppercase characters to lowercase.
`S.title()`	Translates the first letter of each word to uppercase, and all the others to lowercase.
`S.zfill(width)`	Adds zeros to the left of the string to the length `width`.
`S.ljust(width, fillchar=" ")`	Aligns the line to the left, adding the characters `fillchar` to the right.
`S.rjust(width, fillchar=" ")`	Aligns the line to the right, adding `fillchar` characters to the left.
`S.format(args, *kwargs)`	String formatting (a more modern alternative to `%`).

main.py

Test 1

Test 2

Test 3

Test 4

Test 5

Test 6

Test 7

Test 8

Test 9

Test 10

Solution du développeur

# Список стоп-слов, которые нужно удалить. Он задан прямо в коде.
stop_words = ["купить", "цена", "сколько", "стоит", "в", "и", "с", "на"]

# Получаем строку с ключевыми словами от пользователя
keywords_input = input()

# Разделяем полученную строку на отдельные слова по пробелу. Результатом будет список слов.
words = keywords_input.split()

# Создаем пустой список, куда будем складывать "чистые" ключевые слова
clean_words = []

# Запускаем цикл, который перебирает каждое слово в списке 'words'
for word in words:
    # Приводим слово к нижнему регистру для корректного сравнения со списком stop_words
    # и проверяем, НЕ содержится ли оно в списке стоп-слов.
    if word.lower() not in stop_words:
        # Если слово не является стоп-словом, добавляем его в наш список 'clean_words'
        clean_words.append(word)

# Используем метод join, чтобы объединить все элементы списка 'clean_words' в одну строку.
# В качестве разделителя указываем ", " (запятая и пробел).
result = ", ".join(clean_words)

# Выводим итоговую строку на экран
print(result)

🎉 Félicitations ! 🎉

Tu as brillamment résolu la tâche ! C était difficile, mais tu as trouvé la bonne solution. Tu es encore plus proche de maîtriser la programmation ! Continue ainsi.