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PCAP-31-03: How Does Python’s join() and split() Affect List Membership?

By: Author Alex Lim

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Categories Exam

Explore the intricacies of Python string manipulation with join() and split() methods, and learn how they impact list operations in this PCAP-31-03 exam question breakdown.

Table of Contents

Question

What is the expected behavior of the following code?

the_string = ',,'.join(('alpha', 'omega'))
the_list = the_string.split(',')
print(',' in the list)

A. it outputs False
B. it raises an exception
C. it outputs True
D. it outputs nothing

Answer

C. it outputs True

Explanation

Let’s break down the code step by step to understand why:

  1. `the_string = ‘,,’.join((‘alpha’, ‘omega’))`
    This line joins the tuple `(‘alpha’, ‘omega’)` using ‘,,’ as the separator. The resulting string is ‘alpha,,omega’.
  2. `the_list = the_string.split(‘,’)`
    This line splits `the_string` at every occurrence of ‘,’. Since there are two consecutive commas, this results in a list with an empty string between ‘alpha’ and ‘omega’. The resulting list is `[‘alpha’, ”, ‘omega’]`.
  3. `print(‘,’ in the_list)`
    This line checks if the string ‘,’ is present in `the_list`. It’s important to note that this is checking for the comma as a list element, not as a character within the elements.

Although there’s no comma as a separate element in the list, Python evaluates this expression as `True` because an empty string `”` is present in the list. In Python, an empty string is considered a “falsy” value, but it still exists as a distinct element in the list.

This question tests your understanding of:

  • The `join()` method for strings
  • The `split()` method for strings
  • List operations and membership testing
  • How empty strings are handled in lists

It’s a tricky question because it relies on the subtle behavior of `split()` when consecutive delimiters are present in the string being split. This is an important concept to understand for the PCAP-31-03 certification exam and for Python programming in general.

Python Institute PCAP-31-03 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Python Institute PCAP-31-03 exam and earn Python Institute PCAP-31-03 certification.