you are working on the creation of the registration module for the new application "Codefriends". To ensure basic security, you need to write a program that analyzes the password introduced by the user and classifies its reliability.
rnclassification rules for classification rules Password:
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@, & nbsp; # write a program that requests a password and displays the result of its verification.
Password introduced by the user.
The result of a password check (String).
mypassword123
Reliable password
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.
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 %). |
# Получаем пароль от пользователя
password = input()
# Если строка пустая, выводим сообщение и завершаем работу
if not password:
print("Пароль не может быть пустым")
else:
# Флаги для отслеживания типов символов в пароле
has_letter = False # Есть ли хотя бы одна буква
has_digit = False # Есть ли хотя бы одна цифра
has_other = False # Есть ли хотя бы один другой символ
# Перебираем каждый символ в строке пароля
for char in password:
# Проверяем, является ли символ буквой
if char.isalpha():
has_letter = True
# Если не буква, проверяем, является ли он цифрой
elif char.isdigit():
has_digit = True
# Если это не буква и не цифра, значит это другой символ
else:
has_other = True
# Анализируем флаги и выводим результат
# Если найден недопустимый символ, пароль не принимается
if has_other:
print("Недопустимый пароль")
# Если есть и буквы, и цифры (и нет других символов)
elif has_letter and has_digit:
print("Надежный пароль")
# Если есть только буквы (и нет других символов)
elif has_letter:
print("Слабый пароль")
# Если есть только цифры (и нет других символов)
elif has_digit:
print("Слабый пароль")1 - Read the task and understand what needs to be done
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