Why XPath with contains and starts-with in Selenium Python? - Purpose & Use Cases

The Big Idea

What if your tests could find buttons even when their names change a little?

The Scenario

Imagine you have a huge webpage with many buttons and links. You want to click a button, but its exact name changes often, like 'Submit Form 1', 'Submit Form 2', and so on. Manually searching for the exact button each time is like finding a needle in a haystack.

The Problem

Manually writing exact names or full paths for each element is slow and breaks easily when the page changes. You might miss some buttons or click the wrong one, causing errors and frustration.

The Solution

Using XPath with contains and starts-with lets you find elements by parts of their names or attributes. This means your tests keep working even if the full text changes, making your automation smarter and more reliable.

Before vs After

✗ Before

driver.find_element(By.XPATH, "//button[text()='Submit Form 1']")

✓ After

driver.find_element(By.XPATH, "//button[contains(text(), 'Submit Form')]")

What It Enables

This lets you write flexible tests that adapt to small changes in the webpage without breaking.

Real Life Example

When testing a shopping site, product names might change slightly. Using contains helps you find the 'Add to Cart' button even if the product name updates.

Key Takeaways

Manual exact matching is fragile and slow.

contains and starts-with make element finding flexible.

Tests become more reliable and easier to maintain.

Practice

1. Which XPath function would you use to find an element whose id attribute contains the text "submit" anywhere inside it?

easy

A. starts-with(@id, 'submit')

B. contains(@id, 'submit')

C. ends-with(@id, 'submit')

D. equals(@id, 'submit')

Solution

1. Step 1: Understand the contains() function

   The contains() function checks if an attribute or text includes a specific substring anywhere inside it.

2. Step 2: Apply contains() to the id attribute

   Using contains(@id, 'submit') finds elements where the id attribute has 'submit' anywhere in its value.

3. Final Answer:

   contains(@id, 'submit') -> Option B

4. Quick Check:

   contains() = substring anywhere [OK]

Hint: Use contains() to match substring anywhere in attribute [OK]

Common Mistakes:

• Using starts-with() when substring is not at start
• Using ends-with() which is not supported in XPath 1.0
• Using equals() which requires exact match

2. Which of the following is the correct XPath syntax to select elements whose class attribute starts with "btn-"?

easy

A. //element[@class^='btn-']

B. //element[contains(@class, 'btn-')]

C. //element[starts-with(@class, 'btn-')]

D. //element[@class*='btn-']

Solution

1. Step 1: Identify the correct function for 'starts with'

   The starts-with() function is used to check if an attribute value begins with a specific substring.

2. Step 2: Check XPath syntax

   The correct syntax is //element[starts-with(@class, 'btn-')]. Options C and D use invalid XPath syntax for this purpose.

3. Final Answer:

   //element[starts-with(@class, 'btn-')] -> Option C

4. Quick Check:

   starts-with() = prefix match [OK]

Hint: Use starts-with() for prefix matching in XPath [OK]

Common Mistakes:

• Using contains() instead of starts-with() for prefix
• Using CSS selector syntax like ^= or *= in XPath
• Missing parentheses in function call

3. What will be the result of this XPath query?

//div[contains(text(), 'Error') and starts-with(@class, 'alert-')]

Assuming the HTML contains:

<div class="alert-danger">Error: Invalid input</div>
<div class="alert-success">Success</div>
<div class="message-error">Error occurred</div>

medium

A. Selects only the div with class 'alert-danger'

B. Selects no elements

C. Selects all div elements containing 'Error'

D. Selects the first and second div elements

Solution

1. Step 1: Analyze contains(text(), 'Error')

   This matches div elements whose visible text includes 'Error'. The first and third divs contain 'Error'.

2. Step 2: Analyze starts-with(@class, 'alert-')

   This matches div elements whose class attribute starts with 'alert-'. The first and second divs match this.

3. Step 3: Combine both conditions with AND

   Only the first div satisfies both: text contains 'Error' and class starts with 'alert-'.

4. Final Answer:

   Selects only the div with class 'alert-danger' -> Option A

5. Quick Check:

   AND filters to first div only [OK]

Hint: AND requires both conditions true for selection [OK]

Common Mistakes:

• Assuming contains() matches attribute instead of text
• Ignoring the starts-with() condition
• Selecting all divs with 'Error' ignoring class prefix

4. You wrote this XPath to find buttons starting with "save":

//button[contains(@id, 'save-')]

But it also matches buttons with id "disable-save". How to fix it?

medium

A. //button[starts-with(@id, 'save-')]

B. //button[contains(text(), 'save-')]

C. //button[@id='save-']

D. //button[ends-with(@id, 'save-')]

Solution

1. Step 1: Understand why contains() matches unwanted ids

   contains(@id, 'save-') matches any id containing 'save-' anywhere, including 'disable-save'.

2. Step 2: Use starts-with() to match only ids beginning with 'save-'

   starts-with(@id, 'save-') ensures only ids starting exactly with 'save-' are matched.

3. Final Answer:

   //button[starts-with(@id, 'save-')] -> Option A

4. Quick Check:

   starts-with() fixes unwanted matches [OK]

Hint: Use starts-with() to avoid partial matches inside strings [OK]

Common Mistakes:

• Using contains() when prefix match is needed
• Using ends-with() which XPath 1.0 does not support
• Matching text() instead of attribute

5. You want to select all <a> elements where the href attribute starts with "https://" and the link text contains "Learn". Which XPath expression correctly does this?

hard

A. //a[contains(@href, 'https://') and contains(text(), 'Learn')]

B. //a[contains(text(), 'https://') and starts-with(@href, 'Learn')]

C. //a[starts-with(text(), 'Learn') and contains(@href, 'https://')]

D. //a[starts-with(@href, 'https://') and contains(text(), 'Learn')]

Solution

1. Step 1: Match href attribute starting with 'https://'

   Use starts-with(@href, 'https://') to ensure href begins exactly with 'https://'.

2. Step 2: Match link text containing 'Learn'

   Use contains(text(), 'Learn') to find links whose visible text includes 'Learn' anywhere.

3. Step 3: Combine both conditions with AND

   Both conditions must be true, so use and between them.

4. Final Answer:

   //a[starts-with(@href, 'https://') and contains(text(), 'Learn')] -> Option D

5. Quick Check:

   starts-with() + contains() combined correctly [OK]

Hint: Combine starts-with() for attribute and contains() for text [OK]

Common Mistakes:

• Using contains() for href prefix instead of starts-with()
• Swapping text() and attribute in functions
• Using starts-with() on text when contains() is needed