Python - String startswith()

startswith() method in Python 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 data
• Validating input
• Simple pattern matching

Let’s understand by taking a simple example:

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

False

Explanation: startswith() method checks if the string s starts with "for", and since it starts with "Geeks" instead of for, the result is False.

Syntax

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

Parameters:

• prefix: A string or a tuple of strings to check at the start.
• start (optional): Index to start checking from.
• end (optional): Index to stop checking.

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

Example 1: Basic Prefix Check

Here’s a simple example where we check if a given string starts with the word "for".

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

False

Explanation: The string starts with "Geeks", so it returns True.

Example 2: Using start Parameter

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

s = "GeeksforGeeks"
print(s.startswith("for", 5))

True

Explanation: We're checking from index 5, and "for" starts from there hence the result is True.

Example 3: Using start and end Parameters

We can also check for stings within a given slice using star and end parameters.

s = "GeeksforGeeks"
print(s.startswith("for", 5, 8))

True

Explanation: checking only between index 5 and 8 (non inclusive) and "for" lies in that slice, so it returns True.

Example 4: 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".
• The string starts with "Geeks", which is one of the options in the tuple, so the result is True.