str.isalpha()

str.isalpha()

The .isalpha() method checks whether all characters in a string are alphabetic letters and the string contains at least one character. It returns a boolean value, making it useful for validating user input, checking string types, and filtering data based on character composition.

This method is part of Python’s suite of string classification methods. Unlike .isdigit() which only accepts numbers, or .isalnum() which accepts both letters and numbers, .isalpha() is stricter—it only returns True for pure alphabetic strings.

Syntax

str.isalpha()

Parameters

This method takes no parameters.

Examples

Basic usage

text = "Hello"
print(text.isalpha())
# True

with_space = "Hello World"
print(with_space.isalpha())
# False (space is not alphabetic)

with_number = "Hello123"
print(with_number.isalpha())
# False (numbers are not alphabetic)

Empty strings return False

empty = ""
print(empty.isalpha())
# False

# This is important for validation logic
# An empty string has no alphabetic characters

Special characters fail the check

with_underscore = "hello_world"
print(with_underscore.isalpha())
# False

with_hyphen = "hello-world"
print(with_hyphen.isalpha())
# False

with_punctuation = "Hello!"
print(with_punctuation.isalpha())
# False

Common Patterns

Validating names

def is_valid_name(name):
    """Check if name contains only alphabetic characters."""
    if not name:
        return False
    return name.isalpha()

print(is_valid_name("John"))
# True
print(is_valid_name("John Doe"))
# False (space not allowed)
print(is_valid_name("Maria"))
# True
print(is_valid_name(""))
# False

Processing input lists

words = ["hello", "world123", "test!", "python", "code2"]

# Filter to only alphabetic words
alphabetic = [w for w in words if w.isalpha()]
print(alphabetic)
# ['hello', 'python']

Combining with other checks

def is_proper_noun(word):
    """Check if word is alphabetic and starts with uppercase."""
    if not word or not word.isalpha():
        return False
    return word[0].isupper()

print(is_proper_noun("London"))
# True
print(is_proper_noun("london"))
# False
print(is_proper_noun("London2"))
# False

Unicode Support

Python 3 treats Unicode letters as alphabetic. This includes characters from many writing systems beyond the basic Latin alphabet:

# Latin letters work as expected
print("Python".isalpha())
# True

# Greek letters are also alphabetic
greek = "Πύθων"
print(greek.isalpha())
# True

# Cyrillic letters work too
cyrillic = "Питон"
print(cyrillic.isalpha())
# True

# Chinese characters are considered alphabetic in Python
chinese = "Python语言"
print(chinese.isalpha())
# False (mixed scripts)

# Emoji are not alphabetic
emoji = "👋"
print(emoji.isalpha())
# False

Behavior Notes

• Returns False for empty strings—the string must contain at least one character
• Returns True for strings containing only alphabetic Unicode characters
• Does not check for spaces, numbers, punctuation, or mixed character types
• Unicode category “Lm”, “Lt”, “Lu”, “Ll”, “Lo”, or “Lt” characters are considered alphabetic

See Also

• str.isalnum()
• str.isascii()
• str.isdecimal()