NumPy — Creation#
| Function |
Result |
np.array(x) |
from list |
np.arange(a,b,s) |
range by step |
np.linspace(a,b,n) |
range by count |
np.zeros/ones/full/empty(shape) |
filled arrays |
np.eye(n)/identity(n) |
identity |
np.random.default_rng(seed) |
RNG |
NumPy — Manipulation#
| Function |
Result |
reshape / ravel / flatten |
change shape |
.T / transpose / swapaxes |
reorder axes |
expand_dims / squeeze |
add/drop axes |
concatenate / stack / vstack / hstack |
combine |
split / array_split |
divide |
NumPy — Compute#
| Function |
Result |
sum/mean/std/min/max (axis=) |
reductions |
sort/argsort/argmax/argmin |
order |
where / nonzero / unique / clip |
select/transform |
dot / @ / matmul |
matrix mult |
linalg.inv/det/solve/eig/svd/norm |
linear algebra |
Pandas — Inspect#
| Method |
Result |
head/tail/sample |
peek rows |
info/describe/dtypes/shape |
overview |
value_counts/nunique/unique |
categories |
isna().sum() |
missing count |
Pandas — Select#
| Method |
Result |
loc[label] / iloc[pos] |
rows |
df[mask] / query() |
filter |
isin / between / where / mask |
conditional |
at / iat |
fast scalar |
| Method |
Result |
fillna/dropna/replace |
missing |
drop_duplicates |
dedupe |
astype/to_numeric/to_datetime |
types |
assign/apply/map/pipe |
columns |
rename/drop/insert |
structure |
Pandas — Aggregate & Reshape#
| Method |
Result |
groupby().agg/transform/filter |
split-apply-combine |
merge/join/concat |
combine |
pivot_table/melt/stack/unstack/crosstab |
reshape |
sort_values/nlargest/nsmallest |
order |
rolling/expanding/ewm/resample |
windows & time |
The 20 functions you will use most#
read_csv, head, info, describe, loc, iloc, groupby, agg,
merge, pivot_table, fillna, dropna, value_counts, sort_values,
apply, astype, to_datetime, rolling, np.where, np.array.
📌 Final word: The two skills that separate beginners from professionals are
(1) thinking in vectors — replacing loops with array/column operations, and
(2) mastering the split-apply-combine pattern with groupby + transform/agg.
Everything else is vocabulary. Practice the exercises until these two feel automatic.
End of handbook.