Python syntax map¶

Use this as a lookup after the course gives you a reason for the syntax.

Bind a name¶

radius_m = 1e-3

The name now refers to a value. Python does not encode units, so the name or a units library must.

cases = ["c001", "c002", "c003"]

Lists are ordered and mutable. Tuples are ordered and normally used for fixed records:

limits = (0.0, 1.0)

summary = {"peak_energy": 0.194, "final_time": 0.75}
summary["peak_energy"]

if time_step <= 0:
    raise ValueError("time step must be positive")
elif time_step < warning_limit:
    warn()
else:
    continue_normally()

Indentation defines the block.

for case in cases:
    process(case)

Use enumerate when both index and item matter:

for index, value in enumerate(values):
    ...

Use while when termination depends on changing state:

while residual > tolerance:
    state = update(state)

Always plan a maximum iteration count.

def weber(density, speed, length, surface_tension):
    return density * speed**2 * length / surface_tension

Keyword-only policy arguments follow *:

def detect(values, *, window=4, tolerance=0.02):
    ...

raise ValueError("Oh must be positive")

Catch only errors you can handle:

try:
    value = float(text)
except ValueError as error:
    raise ValueError(f"bad value: {text!r}") from error

from pathlib import Path

path = Path("data") / "log.csv"
text = path.read_text(encoding="utf-8")

For structured CSV, use csv.DictReader, NumPy, or pandas with a declared schema.

import numpy as np

time = np.linspace(0.0, 1.0, 101)
late = time > 0.5
late_time = time[late]

Important attributes:

time.shape
time.ndim
time.dtype
time.size

from comphy_python101 import load_basilisk_log

The imported name becomes available in the current module. Avoid wildcard imports; they hide provenance.

def main():
    ...
    return 0


if __name__ == "__main__":
    raise SystemExit(main())

This lets the file act as a command while keeping functions importable for tests.

def test_length_scaling():
    assert second / first == pytest.approx(2**1.5)

The test name states the claim. pytest.approx handles floating-point comparison with a tolerance.

message = f"case {case_id}: peak={peak:.3g}"

Use formatting for presentation, not before numerical operations.

def summarise(path: Path) -> dict[str, float]:
    ...

Hints document intent and help tools. Python does not enforce them at runtime. Validation is still required at external boundaries.