理论与实践

数据输入输出

任务

条件语句

任务

for循环

任务

字符串

任务

while循环

任务

列表

任务

二维数组

任务

字典

任务

集合

任务

函数与递归

任务

课程 4. Lines

难度：

任务«SEO优化»

💻 Python

你在一家互联网公司找到了一份初级SEO专员的工作。你的第一个任务——帮助优化客户网站。你获得了一个关键词列表，但它非常“脏”：包含大量垃圾词（所谓的“停用词”），例如连词、介词以及像“购买”或“价格”这类不承载特定页面主要语义的通用请求。

你的任务——编写一个程序，从原始字符串中清除这些停用词，并从剩余的“干净”关键词中形成一个新的字符串，这些关键词将通过逗号列出。这将有助于进一步在网站的元标签中使用它们。

技术要求：

程序必须接收一行由空格分隔的关键词组成的字符串。
程序内部应硬编码一个停用词列表（例如：“购买”、“价格”、“多少钱”、“值”、“在”、“和”、“与”、“上”）。
程序必须将输入的字符串拆分成单独的单词。
使用循环 for ，程序应遍历所有单词。
使用条件 if ，对每个单词检查它是否为停用词。检查应不区分大小写（即“购买”和“购买”是同一个停用词）。
不是停用词的单词（即它们是干净的）应收集到一个单独的列表中。
最后，程序应输出一行由干净单词通过逗号和空格（, ）连接而成的字符串。如果没有剩余干净单词，程序应输出一个空字符串。

输入格式

一行（字符串）包含关键词，以空格分隔。

输出格式

字符串（String），包含过滤后的关键词，以逗号和空格分隔。

示例

输入

在莫斯科购买华硕笔记本电脑的价格

输出

笔记本电脑，华硕，莫斯科

提示

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

测试 1

测试 2

测试 3

测试 4

测试 5

测试 6

测试 7

测试 8

测试 9

测试 10

开发者解答

# 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)