Python – String startswith()

startswith() method in Python is a built-in string method that checks whether a given string starts with a specific prefix. It helps in efficiently verifying whether a string begins with a certain substring, which can be useful in various scenarios like filtering or validating input. In this article, we will understand about startswith() method.

Let’s understand by taking a simple example:

s = "GeeksforGeeks"
res = s.startswith("for")

print(res)  

False

Explanation:

• We create a string 's' with the value "GeeksforGeeks!".
• We then call the startswith() method on 's', passing "Geeks" as the prefix.
• The method checks if the string starts with "Geeks", and since it does, the result is True.

Syntax of startswith() method

string.startswith(prefix[, start[, end]])

Parameters:

• prefix: The substring or a tuple of substrings to check for at the start of the string.
• start (optional): The index where the search for the prefix begins. By default, it starts from index 0.
• end (optional): The index where the search for the prefix ends. If not specified, the search goes till the end of the string.

Return Type:

• The method returns a Boolean:
  • True if the string starts with the specified prefix.
  • False if it does not.

Examples of startswith() method

Basic Prefix Check

Here’s a simple example where we check if the string starts with the word “Python”.

s = "GeeksforGeeks"

res = s.startswith("for")
print(res)  

False

• Explanation: The string starts with the word "Python", so the method returns True.

Using start and end Parameters

Let’s check the string using the start parameter to begin from a specific index.

s = "GeeksforGeeks"

res = s.startswith("for", 9)
print(res) 

False

Explanation:

• We start the check from index 9, where "Python" begins in the string.
• The method returns True because the substring at that position is "Python".

3. Checking Multiple Prefixes

We can also check if the string starts with any one of several prefixes by passing a tuple of prefixes.

s = "GeeksforGeeks"

res = s.startswith(("Geeks", "G"))
print(res)

True

Explanation:

• We pass a tuple with two prefixes: "Geeks" and "G".
• Since the string starts with "Geeks", the method returns True.

FAQ’s on String startswith()

Can startswith() check multiple prefixes?

Yes, we can pass a tuple of prefixes, and it will return True if the string starts with any one of them.

What happens if we pass invalid start and end indices?

If the start or end index is out of bounds, it will raise an IndexError.

Does the method modify the original string?

No, the startswith() method only checks the prefix and returns a Boolean value. It doesn’t modify the string.

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Article Tags :

• Python
• python-string

Practice Tags :

• python