PCEP Control Flow, Loops, Lists and Logic Practice Question

A developer needs to iterate over a list of network interfaces and print only the names that start with 'eth'. Which code should be used?

⚠ Common exam trap

Python Institute often tests the distinction between `in` (substring membership) and `startswith()` (prefix matching), leading candidates to choose Option D because they think 'eth' must appear at the start, but `in` would also match names like 'xeth0'.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

for iface in interfaces: if iface.startswith('eth'): print(iface)

The `startswith()` string method is the most direct and readable way to check if each interface name begins with the substring 'eth'. This approach avoids unnecessary slicing or substring membership checks, making the intent clear and the code efficient.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
for i in range(len(interfaces)): if 'eth' in interfaces[i]: print(interfaces[i])
Why it's wrong here
Same as B, substring check.
✗
for iface in interfaces: if iface[:3] is 'eth': print(iface)
Why it's wrong here
'is' compares identity, not equality; incorrect for strings.
✓
for iface in interfaces: if iface.startswith('eth'): print(iface)
Why this is correct
Correct; startswith checks prefix.
✗
for iface in interfaces: if 'eth' in iface: print(iface)
Why it's wrong here
Checks substring anywhere, not just start.

Go deeper

PCEP Control Flow, Loops, Lists and Logic Practice Question

Why each option matters

Option-by-option breakdown

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