Position size from stop distance

easyTradingacceptance —~10 min

Implement position_size(equity, risk_frac, entry, stop) — the number of WHOLE shares to buy so that being stopped out loses at most equity·risk_frac: floor(equity·risk_frac / |entry - stop|).

Risk a fixed fraction per trade and let the stop set the size — the rule the safety settings on this site enforce for you. Return an integer.

example 1

input

equity=10000.0, risk_frac=0.01, entry=50.0, stop=48.0

output

note

Risking $100 at $2 per share buys 50 shares.

example 2

input

equity=10000.0, risk_frac=0.01, entry=50.0, stop=47.6

output

constraints

equity > 0
0 < risk_frac ≤ 0.05
entry != stop

teacher · 2 hints · the first is free

↗ read the theory

the chapter this problem is cut from

▶ open in the workbench

run the same math on a real tape

●solution.py· utf-8 · spaces:4

def position_size(equity: float, risk_frac: float, entry: float, stop: float) -> int:
    """Whole shares such that a stop-out loses at most equity × risk_frac."""
    per_share = abs(entry - stop)
    # TODO: whole shares — floor the result instead of returning a fraction
    return equity * risk_frac / per_share

ln 1, col 1tab indent · esc leave editor

python 3.13 · pyodide

+ 6 hidden on submit

input · keyword arguments to position_size()

equity=10000.0, risk_frac=0.01, entry=50.0, stop=48.0

expected

the judge calls position_size() with exactly these inputs · outputs are compared to 6 decimal places

● standing bypython 3.13 in your browser · pyodide 0.28.3 · judged on the server to 6 dp⌘↵ run · ⌘⇧↵ submit

paper only · educational · not advice