Checking for Uppercase Letters in Python A string is considered to contain only upper-case letters if all its characters are alphabets and each one is in upper case (from 'A' to 'Z'). Python provides various ways to check this, such as using the isupper() method, regular expressions, or manually checking each character. Using isupper() Method The isupper() method returns True if all the alphabetic characters in the string are uppercase and there is at least one alphabet. If the string contains any lowercase letters or non-alphabetic characters, it returns False. Example: All Uppercase Letters In the following example, the string ... Read More

Checking for Lowercase Letters in PythonIn Python, a string is considered to have only lower-case letters if all its characters are alphabets and each one of them is in lower case (from 'a' to 'z'). We can verify this using the built-in islower() method, regular expressions, or by checking each character using the all() method. Using islower() Method The islower() method returns True if all the characters in the string are in lowercase and there is at least one alphabet. If the string contains uppercase letters or non-alphabetic characters, it returns False. Example: All Lowercase Letters In the following example, ... Read More

In Python, Unicode strings can contain numeric characters from various languages and scripts. To check if a Unicode string contains only numeric characters, we can use built-in string methods, regular expressions, or character iteration. These methods ensure that characters like Arabic numerals, Chinese digits, or superscripts are also recognized as valid numeric characters. Using isnumeric() Method The isnumeric() method returns True if all characters in the string are numeric, including Unicode numeric characters like ², ١, 一, etc. If any character is non-numeric or the string is empty, it returns False. Example: Unicode Numeric Characters In the following example, ... Read More

To check if a Python string contains only certain characters, you can use - set Comparison Regular Expressions Character Lists These approaches help you to verify whether every character in the string belongs to a defined set of allowed characters or not. Using Set Comparison You can create a set of allowed characters and check if all characters in the string belong to that set or not. If the string is a subset of the allowed set, it means the string contains only valid (accepted) characters. Example In the following example, we define a set of allowed numeric ... Read More

To check if a Python string contains only digits, you can use the built-in isdigit() method. This method returns True if all characters in the string are digits, and False otherwise. Besides isdigit(), you can also use loops or regular expressions to verify this condition. Using the isdigit() Method The isdigit() method is used to check if a string contains only digits. It returns True only when every character is a digit. Example In this example, we define a string that contains only digits and use the isdigit() method to check it. The output confirms that the string contains only ... Read More

In this article, we focus on how to check if a string is alphanumeric using regular expressions in Python. Regular expressions are very useful for pattern matching and validation. To use them, first import the re library, which is included by default in Python. The regular expression ^[a-zA-Z0-9]+$ matches strings that contain only letters (both uppercase and lowercase) and numbers. This expression returns True if the string is alphanumeric; otherwise, it returns False. Using Regular Expressions By applying the re.match() function with the above pattern, you can check if the entire string contains only alphanumeric characters. Example: Checking an Alphanumeric ... Read More

In Python, strings can contain letters, numbers, or special characters. To check if a string is alphanumeric (contains only letters and numbers), we can use different methods. This article shows three simple ways to do that: Using the isalnum() function Using regular expressions Using the isalpha() and isdigit() functions Using the isalnum() Function The isalnum() method returns True if all characters in the string are letters or digits; otherwise, it returns False. Example: Basic Alphanumeric Check In the example below, we take two strings and check if they contain only alphabets and numbers using the isalnum() function: str1 ... Read More

To verify that a string contains only letters, numbers, underscores, and dashes in Python - Use re.fullmatch() function with a pattern like [A-Za-z0-9_-]+ for regex-based checking. Use set comparison with all() function for simple logic-based validation. Many systems restrict input to certain characters for security or formatting reasons. In this case, the allowed characters are alphabets (A–Z, a–z), digits (0–9), underscores (_), and hyphens (-). Using Regular Expressions The re module in Python allows you to define patterns to validate strings. You can use re.fullmatch() function to check if the entire string matches a specific pattern, such as ... Read More

To check if a string contains at least one letter and one number in Python, you can - Use any() function with str.isalpha() function and str.isdigit() function to go through characters. Use re.search() function with appropriate regular expressions for pattern matching. Both methods are commonly used for validating input strings where letters and digits are required. Using any() Function with String Methods The any() function can be combined with str.isalpha() or str.isdigit() functions to check if at least one character in the string is a letter or a digit. This approach is used for partial checks within ... Read More

In Python, you can check whether a string contains letters, numbers, or both using built-in string methods such as isalpha(), isdigit(), and isalnum(). You can also use loops or regular expressions for more customized checks. Checking for Only Alphabets The isalpha() method returns True if every character in the string is a letter (a–z or A–Z) and the string is not empty. It is useful for validating names or inputs that should contain only alphabets. Example In this example, we check if the string has only alphabets using the isalpha() method - text = "HelloWorld" print(text.isalpha()) The string returns ... Read More