Free Python interview prep

From “I’ve read about it” to “I can solve it and explain it”

For Python developers, from fresher to six years in. Learn each topic step by step, write code in the page, and practice saying it out loud.

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Two Sum · DSA foundations

OkayBetterBest

Check every pair O(n²)

def two_sum(nums: list[int], target: int) -> list[int]:
    for i in range(len(nums)):
        for j in range(i + 1, len(nums)):
            if nums[i] + nums[j] == target:
                return [i, j]
    return []

Too slow for 100,000 numbers

Sort, then two pointers O(n log n)

def two_sum(nums: list[int], target: int) -> list[int]:
    pairs = sorted((value, i) for i, value in enumerate(nums))
    lo, hi = 0, len(pairs) - 1
    while lo < hi:
        total = pairs[lo][0] + pairs[hi][0]
        if total == target:
            return sorted([pairs[lo][1], pairs[hi][1]])
        if total < target:
            lo += 1
        else:
            hi -= 1
    return []

Faster, but sorting is extra work

One pass with a dict O(n)

def two_sum(nums: list[int], target: int) -> list[int]:
    seen: dict[int, int] = {}  # value -> index
    for i, num in enumerate(nums):
        partner = target - num
        if partner in seen:
            return [seen[partner], i]
        seen[num] = i
    return []

One pass. The answer to give

Pick your level

Not sure where to begin? Pick the line that sounds like you. Each one names the first topic to open and what comes after. Want a plan that fits your job and your interview date? Answer four questions.

Fresher, or new to Python
About 12 h
First topic: Install Python and run your first file (Python)
Then: Python foundations → DSA foundations → SQL foundations → Interview Playbook foundations
Route details and tips
Then follow the route for 2 to 3 years of experience.
Go in order. Every topic only needs the ones before it. About 12 h of reading, or 25 to 37 h with practice.
Start here : Install Python and run your first file
2 to 3 years of experience
About 17 h
First topic: Names, objects and references (Python)
Then: Python core → DSA core → SQL core → System Design foundations
Route details and tips
Not sure you can skip the basics? Check Python foundations (15 questions), DSA foundations (9 questions) or SQL foundations (15 questions).
Then follow the route for 5 to 6 years of experience.
Take the foundations checks first, and skip every topic they mark Known. About 17 h of reading, or 33 to 50 h with practice.
Start here : Names, objects and references
5 to 6 years of experience
About 21 h
First topic: The system design interview framework (System Design)
Then: System Design core → System Design advanced → DSA: the topics asked often → Python advanced → Scenarios core
Route details and tips
Not sure you can skip the basics? Check Python foundations (15 questions) or DSA foundations (9 questions).
Design rounds weigh most at this level, but coding rounds still happen. Learn the shape of the design round first, then fill the gaps. About 21 h of reading, or 42 to 63 h with practice.
Start here : The system design interview framework
Interview in the next two weeks
About 20 h
First topic: How interview loops work (Interview Playbook)
Then: Python: the topics asked often → DSA: the topics asked often → SQL: the topics asked often → Interview Playbook foundations
Route details and tips
Cover what interviews ask most. These links open each roadmap with "Asked often only" on. About 20 h of reading, or 41 to 61 h with practice.
Start here : How interview loops work

How it works

Every lesson starts with an everyday problem. Then it climbs three steps, from a simple answer to the best one:

Okay
The first idea most people have. It works, and you see where it struggles.
Two Sum: Check every pair: O(n²)
Better
Spot the wasted work and fix it with one new idea.
Two Sum: Sort, then two pointers: O(n log n)
Best
The best answer, and when it is not the right choice.
Two Sum: One pass with a dict: O(n)

Then you practice:

Write the code in the page and run tests. Nothing to install.
Build system designs by drag and drop, and press Check for feedback. Try it.
Say it out loud: what to tell the interviewer, and the follow-up questions you’ll get.
Remember it with a short quiz and flashcards that come back on a schedule.

Eight tracks, in a suggested order

Start from zero, or jump in anywhere. Each track lists every topic in order and says which track to do before it, so you always know what’s next and what you’ve done.

From “I’ve read about it” to “I can solve it and explain it”

Pick your level

Fresher, or new to Python

2 to 3 years of experience

5 to 6 years of experience

Interview in the next two weeks

How it works

Eight tracks, in a suggested order