How can I test if a string starts with a capital letter using Python?

A string is a collection of characters that can represent a single word or a whole sentence. While working with strings, we often need to check whether the string starts with a capital letter. This can be useful for validating names or sentences to ensure they follow certain formatting rules.

Python provides multiple methods to test if a string starts with a capital letter. In this article, we will explore three different approaches to accomplish this task.

Using str.isupper() Method

The isupper() method checks whether all characters in a string are uppercase. To test if a string starts with a capital letter, we can use str[0].isupper() to check just the first character.

Syntax

str.isupper()

Example

Let's check whether the first character is an uppercase letter using str[0].isupper() −

text1 = "Welcome to Tutorialspoint"
text2 = "hello world"

if text1[0].isupper():
    print("Text1: Starts with a capital letter")
else:
    print("Text1: Does not start with a capital letter")

if text2[0].isupper():
    print("Text2: Starts with a capital letter")
else:
    print("Text2: Does not start with a capital letter")

Text1: Starts with a capital letter
Text2: Does not start with a capital letter

Using str.startswith() Method

The startswith() method checks whether a string starts with a specified prefix. We can pass a tuple of all uppercase letters to check if the string begins with any uppercase character.

Syntax

str.startswith(value, start, end)

Example

Here we use string.ascii_uppercase to create a tuple of all uppercase letters −

import string

text1 = "TutorialsPoint"
text2 = "python programming"

if text1.startswith(tuple(string.ascii_uppercase)):
    print("Text1: Starts with a capital letter")
else:
    print("Text1: Does not start with a capital letter")

if text2.startswith(tuple(string.ascii_uppercase)):
    print("Text2: Starts with a capital letter")
else:
    print("Text2: Does not start with a capital letter")

Text1: Starts with a capital letter
Text2: Does not start with a capital letter

Using Regular Expressions

The re module supports regular expressions for pattern matching. We can use re.match() with the pattern [A-Z] to check if the first character is an uppercase letter.

Example

Using a regular expression to match uppercase letters at the beginning −

import re

text1 = "Welcome"
text2 = "welcome"

if re.match(r'[A-Z]', text1):
    print("Text1: Starts with a capital letter")
else:
    print("Text1: Does not start with a capital letter")

if re.match(r'[A-Z]', text2):
    print("Text2: Starts with a capital letter")
else:
    print("Text2: Does not start with a capital letter")

Text1: Starts with a capital letter
Text2: Does not start with a capital letter

Comparison

Conclusion

Use str[0].isupper() for simple cases, startswith() with string.ascii_uppercase for robust validation, and regular expressions when you need complex pattern matching. The startswith() method is generally recommended for production code.