理论与实践

数据输入输出

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条件语句

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for循环

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字符串

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while循环

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列表

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二维数组

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字典

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集合

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函数与递归

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课程 4. line

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任务«引用»

💻 Python

你找到了一句鼓舞人心的名言，并想在社交网络上分享。为了增强效果，你决定在一条消息中重复多次，并在重复之间添加一个空格以提高可读性。然而，如果重复次数为零或负数，则没有意义，你需要得到一条警告信息。

你的任务： 编写一个程序，该程序：

向用户请求一句名言。
向用户请求所需的重复次数。
检查重复次数是否为正数（大于0）。
如果重复次数大于0，程序生成并显示一行，其中名言重复指定次数，并用空格分隔。
如果重复次数为0或更少，程序显示错误消息："重复次数应大于零！"。

输入格式

第一行：励志名言（类型：字符串）。
第二行：重复次数（类型：整数）。

输出格式

一行：包含引号重复的最终行（类型：字符串）或错误信息（类型：行）。

示例

输入

一直向前走！
3

输出

勇往直前！勇往直前！勇往直前！

提示

All about strings in Python: from the basics to useful tricks

A string in Python is an ordered sequence of characters. To create a string, it must be enclosed in single ('...'), double ("...") or even triple quotes ("""...""" or "'..."'), which are especially useful for multi-line texts.

The key feature of strings in Python is their immutability. This means that after creating a string, you cannot change its individual characters. Any operation that "modifies" a row actually creates a new one.

string1 = "Hello, World!"
string2 = 'Python is fun'
# Example of a multiline string
multiline_string = """This is a string
that takes
up several lines of code."""

Indexing of rows

Each character in the string has its own unique number, or index. Indexing allows us to access any single character.

It is important to remember: Indexing in Python always starts with 0, not 1. An attempt to access a non-existent index will cause an error IndexError.

w = "Python"
print(w[0]) # Output: P
print(w[1]) # Output: y
print(w[2]) #Output: t
print(w[3]) # Output: h
print(w[4]) # Output: o (not 0, as in the original example)

There is also negative indexing, which is very convenient for accessing characters from the end of a string, where -1 is the last character, -2 is the penultimate, and so on.

print(w[-1]) # Output: n (last character)
print(w[-2]) # Output: o (penultimate character)

Slicing lines

Slices are a powerful tool for extracting a part of a string (substring). They allow you to get not a single character, but a whole range.

General syntax: string[start : end : step]

start : the index from which the slice begins (this character is included in the result).
end : the index at which the slice ends (this character is not included in the result).
step : determines the interval at which characters should be extracted (the default is 1).

Examples of cross-sections

Substring extraction

string = "Hello, World!"
substring = string[0:5] # Characters 0 through 4 inclusive
print(substring) # Output: Hello

Missing starting or ending index If you omit the initial index, the slice will start from the very beginning of the row. If you omit the final one, it will continue to the very end.

string = "Hello, World!"
substring1 = string[:5] # From the beginning to index 5 (not inclusive)
substring2 = string[7:]   # From index 7 to the end of the line
print(substring1) # Output: Hello
print(substring2) # Output: World!

Using a step The step allows you to "jump over" the symbols. For example, step 2 takes every second character.

string = "Hello, World!"
substring = string[::2] # Every second character from the beginning to the end
print(substring) # Output: Hlo ol!

Negative indexes in slices They can be combined to get the parts of the string from the end.

string = "Hello, World!"
substring = string[-6:-1] # We start with the 6th character from the end and go to the 1st from the end.
print(substring) # Output: World

Useful trick: inverting the string The easiest and most popular way to flip a string is to use a slice with a step -1.

string = "Hello, World!"
reversed_string = string[::-1]
print(reversed_string) # Output: !dlroW ,olleH

Adding and multiplying strings

Addition (concatenation) is performed using the + operator. It "glues" the lines into one new one.

str1 = "Hello"
str2 = "World"
result = str1 + ", " + str2 + "!"
print(result) # Output: Hello, World!

Important advice: You cannot add a string with a number directly. To do this, the number must first be converted to a string using the str() function..

# print("Age: " + 25) # Will cause TypeError
print("Age:" + str(25)) # Correct! Output: Age: 25

Multiplication is performed using the * operator, which repeats the string a set number of times. This is useful for creating separators or formatting.

string = "Go"
result = string * 3
print(result) # Output: GoGoGo
print("-" * 20) # Output: --------------------

Useful string operations

String length The built-in len() function returns the number of characters in a string.

my_string = "Hello"
print(len(my_string))  # Will output: 5

Checking for substring occurrence The in and not in operators allow you to check whether one string is contained inside another. The result will be True or False.

Remember: this check is case-sensitive! 'd' and 'D' are different characters.

name = "Daniil"
password = "Qwerty2000!"
print('D' in name) # Outputs: True
print('d' in name) # Outputs: False
print('3' not in password) # Outputs: True

Iterating through characters in a string

The string can be iterated through in the for loop. There are two main ways, and the choice depends on the task.

Method 1: A simple search (more "pythonic") This method is used when you only need the characters of the string themselves. It's simpler and more readable.

a = "1516 the best"
for char in a: # The char variable sequentially takes the value of each character
    if char in "1234567890":
        print(char)

Method 2: Index search This method is needed when not only the symbol itself is important to you, but also its position (index).

a = "1516 the best"
for i in range(len(a)): #i will take values from 0 to len(a)-1
    if a[i] in "1234567890":
print(f"The character '{a[i]}' was found at position {i}")

Conclusion and what's next?

We have reviewed the basic but very important operations.:

Indexing to access individual characters.
Slices are an incredibly flexible tool for extracting substrings.
Concatenation (+) and repetition (*) to create new strings.

This is the foundation upon which all work with text in Python is based. To move on, study the string methods. These are built-in functions that allow you to do even more useful things with strings, for example:

.lower() / .upper() reduce the entire string to lowercase or uppercase.
.strip() - remove spaces and line breaks at the beginning and at the end.
.replace('old', 'new') replace all occurrences of one substring with another.
.split() - split a string into a list by separator (for example, by space).
.startswith('prefix') / .endswith('suffix') check whether the string begins or ends with a certain sequence of characters.

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

# Получаем цитату от пользователя (это будет строка)
quote = input()
# Получаем количество повторений и сразу преобразуем его в целое число
repetitions = int(input())

# Проверяем, что пользователь ввел положительное число повторений
if repetitions > 0:
    # Создаем пустую строку, в которую будем записывать результат
    result_string = ""
    # Запускаем цикл for, который выполнится столько раз, сколько указал пользователь
    for i in range(repetitions):
        # Добавляем саму цитату к нашей итоговой строке
        result_string += quote
        # Чтобы не ставить лишний пробел в конце, проверяем, не является ли текущее повторение последним
        if i < repetitions - 1:
            # Если это не последнее повторение, добавляем пробел
            result_string += " "
    # Выводим на экран получившуюся строку
    print(result_string)
else:
    # Если условие if не выполнилось (т.е. repetitions <= 0), выводим сообщение об ошибке
    print("Количество повторений должно быть больше нуля!")