you got a job in a large company. Your first task & mdash; Help automate checking files with daily reports. The company has a strict rule: all files with reports should have a name that begins with the prefix & nbsp; report_sales_summary.txt .
you need to write a program that will check the list of file names for compliance with this rule. The program should not open or create files, it works only with their names in the form of lines.
rn task:
Write a program that:
First, the number of files for verification (an integer number) is entered. Then, in each new line, one file name (line) is introduced along one line.
For each entered file name, the verification result is displayed in the new line: "correct" or "incorrect" (line).
4
report_2025.txt
my_report.txt
report_data.csv
report_final_version.txt
correctly
incorrect
incorrect
correctly
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.
1. upper() and lower()
Convert all characters of the string to upper or lower case, respectively.
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RU
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RU
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.
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 %). |
# Запрашиваем у пользователя, сколько имен файлов он хочет проверить
count_str = input()
# Преобразуем полученную строку в целое число (integer)
count = int(count_str)
# Создаем цикл, который будет повторяться 'count' раз
for i in range(count):
# На каждой итерации цикла запрашиваем имя файла
filename = input()
# Проверяем одновременно два условия с помощью 'and':
# 1. filename.startswith("report_") - проверяет, что строка начинается с "report_"
# 2. filename.endswith(".txt") - проверяет, что строка заканчивается на ".txt"
if filename.startswith("report_") and filename.endswith(".txt"):
# Если оба условия выполнены, выводим "Корректно"
print("Корректно")
else:
# Если хотя бы одно из условий не выполнено, выводим "Некорректно"
print("Некорректно")1 - Read the task and understand what needs to be done
2 - The example shows how the input data will be provided and what output is expected
3 - Write the code considering the input, output, and the task itself.
1 - The “Run” button executes your code only on one set of input data, and you’ll see the result in the output window.
2 - The “Test on All Cases” button runs your code against all test cases. If all tests pass, a banner will appear. If even one test fails, it will be highlighted in red.
To change the input data, click the “Run Test” button next to the input data you want to execute.
1 - Input Data is the window containing the values loaded into your program in place of input()
2 - Program Output is the window showing what your program prints. If it’s green, the output matches the expected result; if red, there are differences.
3 - Expected Output is the reference value used to verify the solution.
1 - Green means the program produced the correct output
2 - Red means the program’s output didn’t match the expected output for this data. The program output and the expected output must be identical, including spaces and punctuation!
If you see this banner, congratulations — everything is correct.
1 - The first 10 tasks are quite easy and contain hints covering only the essential parts of the topic.
2 - The next 10 tasks are medium difficulty. Their hints differ from the easy ones and reveal new aspects of the topic.
3 - The hardest tasks have no hints. Often, they include additional topics, so sometimes it’s better to move on and return later. Read the hints carefully — they offer new ways to solve already familiar problems.
1 - Each block contains a “Theory” section.
2 - It always includes a detailed video.
3 - There is also a detailed guide with all the necessary theory and code examples.
1 - Click the “Report an Error / Social Media” button
2 - Here you can describe the error you encountered.
3 - You’ll also find our social media links here — follow us and help us improve.
🎉 Congratulations! 🎉
You did an excellent job with the task! It was a challenging problem, but you found the correct solution. You are one step closer to mastering programming! Keep up the good work, because every stage you pass makes you even stronger.
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