Snapshots, history, and an infinite undo button — the professional way to keep track of your work.
status, log, and diff.gitignore that keeps junk and secrets outAnd why project_v2_final_FINAL is a disaster.
Q3_reserving\
├── reserve_model.xlsx
├── reserve_model_v2.xlsx
├── reserve_model_v2_JS_comments.xlsx
├── reserve_model_v3.xlsx
├── reserve_model_v3_final.xlsx
├── reserve_model_v3_final_FINAL.xlsx
├── reserve_model_v3_final_FINAL_fixed.xlsx
└── reserve_model_USE_THIS_ONE.xlsxFolder-copy versioning answers none of these reliably.
e41c9a2 (HEAD -> main) Use 2025 lapse assumptions in projection
7b0d315 Fix off-by-one in policy-year calculation
c93a8f0 Add IBNR chain-ladder method
5f12e7b Load claims extract from data/raw
a0b3c11 Initial project structureAn audit trail for models: “show me the code that produced the Q3 numbers” becomes a one-line command.
.git\ folder inside your projectAnalogy: Git is like Word’s Track Changes engine; GitHub is like SharePoint for storing and sharing the tracked files.
A GitHub profile, Git for Windows, and your identity.
jane-doe-actuary, not xXdragonslayerXx)Keep your email private: Settings → Emails → tick Keep my email addresses private. GitHub gives you a …@users.noreply.github.com address to use in Git instead.
Work projects with company data belong in your employer’s private organization — never a personal public repo.
winget install --id Git.Git -e --source winget…or download from git-scm.com. The installer has many screens; defaults are fine except:
| Default editor | Pick Notepad or VS Code — not Vim |
| Initial branch name | Override → main |
| PATH | Git from the command line and also from 3rd-party software |
| Line endings | Checkout Windows-style, commit Unix-style |
Then, in a new terminal (the installer changed your PATH):
PS> git --version
git version 2.51.0.windows.1Git for Windows also installs Git Bash (a mini UNIX shell) and Git Credential Manager, which handles GitHub sign-in through your browser.
autocrlf = trueText files mark the end of each line with invisible characters:
| Windows | CR LF (\r\n) |
| Linux / macOS | LF (\n) |
Mix them and every line of a file looks “changed” in Git — even though nothing visibly did.
git config --global core.autocrlf trueCRLF — Windows-friendlyLF — portable for everyonegit config --global user.name "Jane Doe"
git config --global user.email "12345678+jane-doe-actuary@users.noreply.github.com"
git config --global init.defaultBranch main
git config --global core.autocrlf true
git config --global --list # check everythingYour name and email are stamped on every commit you make. Use the same email as your GitHub account (or its noreply address) so commits link to your profile.
--global settings live in C:\Users\Jane\.gitconfig — a plain text file. Open it with notepad ~\.gitconfig.
Working tree → staging area → commit history.
.git\Why a staging area? You edited three files, but only two belong together. Stage those two, commit them with one clear message, then deal with the third separately.
Like preparing a journal entry: you choose which adjustments go into this posting, review them, then post it with a description.
git init and git statusPS C:\actuarial_work\lapse_analytics> git init
Initialized empty Git repository in C:/actuarial_work/lapse_analytics/.git/
PS C:\actuarial_work\lapse_analytics> git status
On branch main
No commits yet
Untracked files:
(use "git add <file>..." to include in what will be committed)
.gitignore
.python-version
README.md
check_env.py
main.py
pyproject.toml
uv.lockgit status is your dashboard. Run it constantly — it always tells you what to do next. (Notice .venv is missing: uv’s .gitignore already excludes it.)
git add and git commitgit add pyproject.toml uv.lock .python-version
git commit -m "Set up uv project with pandas and numpy"
git add main.py check_env.py
git commit -m "Add environment check script"
git add . # stage everything that changed
git commit -m "Describe project in README"| ✗ | stuff, fix, asdf, final |
| ✓ | Add chain-ladder IBNR method |
| ✓ | Fix policy-year off-by-one in lapse rates |
Make atomic commits: one logical change per commit. Write the message as a command: “Add…”, “Fix…”, “Remove…”.
log and diffPS> git log --oneline
3c1e2d4 (HEAD -> main) Describe project in README
9a7b6f0 Add environment check script
51d0e8a Set up uv project with pandas and numpy
PS> git diff
diff --git a/check_env.py b/check_env.py
@@ -12,3 +12,4 @@
df["px"] = 1 - df["qx"]
-print(df)
+df["mu"] = -np.log(df["px"]) # constant force
+print(df.round(5))| Command | Shows |
|---|---|
git status | What’s changed / staged / untracked |
git diff | Unstaged line changes |
git diff --staged | What the next commit will contain |
git log --oneline | Compact history |
git show 9a7b6f0 | One commit in full |
Red - lines were removed; green + lines were added. Press q to exit long output.
| Situation | Command | Risk |
|---|---|---|
| Staged something by mistake | git restore --staged file | Safe — edits kept |
| Want to throw away edits to a file | git restore file | Uncommitted edits are lost |
| Typo in the last commit message (not pushed yet) | git commit --amend -m "…" | Rewrites last commit |
| A committed change was wrong | git revert <commit> | Safe — adds an “undo” commit |
| See an old version of a file | git show a0b3c11:main.py | Read-only |
Once something is committed, it is very hard to lose. Commit early, commit often.
.venv\uv.lock*.pkl.csv.env files. Once pushed, assume they’re compromisedPolicyholder and claims data is personal data. Committing it — especially to a public repo — can be a regulatory breach. Keep data out; commit the code that reads it.
.gitignore tuned for Python & Jupyter# Python / uv
__pycache__/
*.py[oc]
.venv/
build/
dist/
*.egg-info
# Jupyter
.ipynb_checkpoints/# Data & derived artefacts
data/raw/
*.pkl
*.parquet
output/
# Secrets
.env
*.key
credentials*.json
# OS & Office clutter
Thumbs.db
desktop.ini
~$*# starts a commentfolder/ ignores a whole directory* is a wildcard.gitignore itself.gitignore only affects untracked files. If you already committed something, remove it from tracking with git rm --cached file.
Check it works: git status --ignored
lapse_analytics → Private → don’t add a READMEgit remote add origin https://github.com/jane-doe-actuary/lapse_analytics.git
git push -u origin main # first time: a browser window opens so you can sign in
git push # every time after thatcommit saves a snapshot locally. push copies your snapshots to GitHub. They are separate steps.
autocrlf, and default branchC:\actuarial_work\lapse_analytics (Module 4).gitignore for Python/Jupyter and prove it workscd C:\actuarial_work\lapse_analytics
git init # "Reinitialized…" is fine if uv already did it
notepad .gitignore # add the Jupyter / data / secrets sections
mkdir data\raw; Set-Content data\raw\claims.csv "id,amount`n1,1200"
Set-Content .env "API_KEY=not-a-real-key"
git status # claims.csv and .env must NOT appear
git status --ignored # …but they show up here
git add .gitignore
git commit -m "Ignore venv, data, notebook checkpoints and secrets"
git add pyproject.toml uv.lock .python-version
git commit -m "Set up uv project with pandas, numpy, openpyxl"
git add main.py check_env.py README.md
git commit -m "Add starter scripts and README"
git log --onelinecheck_env.py: add a force-of-mortality column mu (see the diff slide)git status → git diff → read the red/green linesgit add check_env.py → git diff --stagedgit log --onelinegit restorewinget install --id Microsoft.VisualStudioCode -e
# new terminal, then:
code .Open the Source Control panel (Ctrl+Shift+G) and click a changed file for a side-by-side diff.
git --version works; name, email, autocrlf are setinit, add, commit, and write a good messagestatus, log --oneline, and diff to inspect state.gitignore excludes .venv, data, pickles, and secretslapse_analytics project has at least 4 commitsPlain-text documents that render beautifully — and notebooks that mix code, results, and prose.