diff --git a/.flake8 b/.flake8
new file mode 100644
index 0000000..2bcd70e
--- /dev/null
+++ b/.flake8
@@ -0,0 +1,2 @@
+[flake8]
+max-line-length = 88
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
new file mode 100644
index 0000000..477218a
--- /dev/null
+++ b/.github/workflows/lint.yml
@@ -0,0 +1,17 @@
+name: Lint
+
+on: [push, pull_request, workflow_dispatch]
+
+permissions:
+  contents: read
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: "3.x"
+      - uses: pre-commit/action@v3.0.0
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..8fff9f1
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,49 @@
+repos:
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v3.4.0
+    hooks:
+      - id: pyupgrade
+        args: [--py38-plus]
+
+  - repo: https://github.com/psf/black
+    rev: 23.3.0
+    hooks:
+      - id: black
+
+  - repo: https://github.com/PyCQA/isort
+    rev: 5.12.0
+    hooks:
+      - id: isort
+
+  - repo: https://github.com/PyCQA/flake8
+    rev: 6.0.0
+    hooks:
+      - id: flake8
+        additional_dependencies:
+          [flake8-2020, flake8-errmsg, flake8-implicit-str-concat]
+
+  - repo: https://github.com/pre-commit/pygrep-hooks
+    rev: v1.10.0
+    hooks:
+      - id: python-check-blanket-noqa
+      - id: python-no-log-warn
+
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.4.0
+    hooks:
+      - id: check-case-conflict
+      - id: check-merge-conflict
+      - id: check-json
+      - id: check-toml
+      - id: check-yaml
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v3.0.0-alpha.9-for-vscode
+    hooks:
+      - id: prettier
+        args: [--prose-wrap=always, --print-width=88]
+
+ci:
+  autoupdate_schedule: quarterly
diff --git a/README.md b/README.md
index 406c90b..d58902c 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,9 @@
 # strava_py
+
 Create artistic visualisations with your exercise data (Python version).
 
-This is a port of the [R strava package](https://github.com/marcusvolz/strava) to Python.
+This is a port of the [R strava package](https://github.com/marcusvolz/strava) to
+Python.
 
 ## Installation
 
@@ -29,7 +31,8 @@ stravavis --help
 
 ### Facets
 
-A plot of activities as small multiples. The concept behind this plot was originally inspired by [Sisu](https://twitter.com/madewithsisu).
+A plot of activities as small multiples. The concept behind this plot was originally
+inspired by [Sisu](https://twitter.com/madewithsisu).
 
 ![facets](https://raw.githubusercontent.com/marcusvolz/strava_py/main/plots/facets001.png "Facets, showing activity outlines")
 
@@ -53,39 +56,56 @@ Elevation profiles superimposed.
 
 ### Calendar
 
-Calendar heatmap showing daily activity distance, using the [calmap](https://pythonhosted.org/calmap/) package. Requires "activities.csv" from the bulk Strava export.
+Calendar heatmap showing daily activity distance, using the
+[calmap](https://pythonhosted.org/calmap/) package. Requires "activities.csv" from the
+bulk Strava export.
 
 ![map](https://raw.githubusercontent.com/marcusvolz/strava_py/main/plots/calendar001.png "Calendar heatmap")
 
 ### Dumbbell plot
 
-Activities shown as horizontal lines by time of day and day of year, facetted by year. Requires "activities.csv" from the bulk Strava export.
+Activities shown as horizontal lines by time of day and day of year, facetted by year.
+Requires "activities.csv" from the bulk Strava export.
 
 ![map](https://raw.githubusercontent.com/marcusvolz/strava_py/main/plots/dumbbell001.png "Dumbbell plot")
 
 ## How to use
 
 ### Bulk export from Strava
-The process for downloading data is described on the Strava website here: [https://support.strava.com/hc/en-us/articles/216918437-Exporting-your-Data-and-Bulk-Export#Bulk], but in essence, do the following:
-                                                                           
+
+The process for downloading data is described on the Strava website here:
+[https://support.strava.com/hc/en-us/articles/216918437-Exporting-your-Data-and-Bulk-Export#Bulk],
+but in essence, do the following:
+
 1. Log in to [Strava](https://www.strava.com/)
-2. Select "[Settings](https://www.strava.com/settings/profile)" from the main drop-down menu at top right of the screen
-3. Select "[My Account](https://www.strava.com/account)" from the navigation menu to the left of the screen.
-4. Under the "[Download or Delete Your Account](https://www.strava.com/athlete/delete_your_account)" heading, click the "Get Started" button.
-5. Under the "Download Request", heading, click the "Request Your Archive" button. ***Don't click anything else on that page, i.e. particularly not the "Request Account Deletion" button.***
+2. Select "[Settings](https://www.strava.com/settings/profile)" from the main drop-down
+   menu at top right of the screen
+3. Select "[My Account](https://www.strava.com/account)" from the navigation menu to the
+   left of the screen.
+4. Under the
+   "[Download or Delete Your Account](https://www.strava.com/athlete/delete_your_account)"
+   heading, click the "Get Started" button.
+5. Under the "Download Request", heading, click the "Request Your Archive" button.
+   **_Don't click anything else on that page, i.e. particularly not the "Request Account
+   Deletion" button._**
 6. Wait for an email to be sent
 7. Click the link in email to download zipped folder containing activities
 8. Unzip files
 
 ### Process the data
 
-The main function for importing and processing activity files expects a path to a directory of unzipped GPX and / or FIT files. If required, the [fit2gpx](https://github.com/dodo-saba/fit2gpx) package provides useful tools for pre-processing bulk files exported from Strava, e.g. unzipping activity files (see Use Case 3: Strava Bulk Export Tools).
+The main function for importing and processing activity files expects a path to a
+directory of unzipped GPX and / or FIT files. If required, the
+[fit2gpx](https://github.com/dodo-saba/fit2gpx) package provides useful tools for
+pre-processing bulk files exported from Strava, e.g. unzipping activity files (see Use
+Case 3: Strava Bulk Export Tools).
 
 ```python
 df = process_data("<path to folder with GPX and / or FIT files>")
 ```
 
-Some plots use the "activities.csv" file from the Strava bulk export zip. For those plots, create an "activities" dataframe using the following function:
+Some plots use the "activities.csv" file from the Strava bulk export zip. For those
+plots, create an "activities" dataframe using the following function:
 
 ```python
 activities = process_activities("<path to activities.csv file>")
diff --git a/RELEASING.md b/RELEASING.md
index a7de41d..31b0898 100644
--- a/RELEASING.md
+++ b/RELEASING.md
@@ -13,7 +13,7 @@ git clone https://github.com/marcusvolz/strava_py
 cd strava_py
 ```
 
-* [ ] (Optional) Create a distribution and release on **TestPyPI**:
+- [ ] (Optional) Create a distribution and release on **TestPyPI**:
 
 ```bash
 python -m pip install -U pip build keyring twine
@@ -30,13 +30,13 @@ python -m pip install -U -i https://test.pypi.org/simple/ stravavis
 stravavis --help
 ```
 
-* [ ] Tag with the version number:
+- [ ] Tag with the version number:
 
 ```bash
 git tag -a v0.0.1 -m "Release 0.0.1"
 ```
 
-* [ ] Create a distribution and release on **live PyPI**:
+- [ ] Create a distribution and release on **live PyPI**:
 
 ```bash
 python -m pip install -U pip build keyring twine
@@ -45,7 +45,7 @@ python -m build
 twine check --strict dist/* && twine upload -r pypi dist/*
 ```
 
-* [ ] Check installation:
+- [ ] Check installation:
 
 ```bash
 python -m pip uninstall -y stravavis
@@ -53,13 +53,14 @@ python -m pip install -U stravavis
 stravavis --help
 ```
 
-* [ ] Push tag:
- ```bash
+- [ ] Push tag:
+
+```bash
 git push --tags
 ```
 
-* [ ] Create a new release: https://github.com/marcusvolz/strava_py/releases/new
+- [ ] Create a new release: https://github.com/marcusvolz/strava_py/releases/new
 
-* [ ] Click "Choose a tag" and select newest.
+- [ ] Click "Choose a tag" and select newest.
 
-* [ ] Click "Auto-generate release notes", amend as required and "Publish release".
+- [ ] Click "Auto-generate release notes", amend as required and "Publish release".
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..5d7bf33
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,2 @@
+[tool.isort]
+profile = "black"
diff --git a/src/stravavis/cli.py b/src/stravavis/cli.py
index 8cd2912..29bed7b 100644
--- a/src/stravavis/cli.py
+++ b/src/stravavis/cli.py
@@ -15,35 +15,57 @@ def main():
     parser.add_argument(
         "--lon_min",
         type=float,
-        help="Minimum longitude for plot_map (values less than this are removed from the data)",
+        help="Minimum longitude for plot_map "
+        "(values less than this are removed from the data)",
     )
     parser.add_argument(
         "--lon_max",
         type=float,
-        help="Maximum longitude for plot_map (values greater than this are removed from the data)",
+        help="Maximum longitude for plot_map "
+        "(values greater than this are removed from the data)",
     )
     parser.add_argument(
         "--lat_min",
         type=float,
-        help="Minimum latitude for plot_map (values less than this are removed from the data)",
+        help="Minimum latitude for plot_map "
+        "(values less than this are removed from the data)",
     )
     parser.add_argument(
         "--lat_max",
         type=float,
-        help="Maximum latitude for plot_map (values greater than this are removed from the data)",
+        help="Maximum latitude for plot_map "
+        "(values greater than this are removed from the data)",
     )
     parser.add_argument(
         "--bbox", help="Shortcut for comma-separated LON_MIN,LAT_MIN,LON_MAX,LAT_MAX"
     )
-    parser.add_argument("--alpha", default=0.4, help="Line transparency. 0 = Fully transparent, 1 = No transparency")
+    parser.add_argument(
+        "--alpha",
+        default=0.4,
+        help="Line transparency. 0 = Fully transparent, 1 = No transparency",
+    )
     parser.add_argument("--linewidth", default=0.4, help="Line width")
-    parser.add_argument("--activities_path", help="Path to activities.csv from Strava bulk export zip")
-    parser.add_argument("--year_min", help="The minimum year to use for the calendar heatmap.")
-    parser.add_argument("--year_max", help="The maximum year to use for the calendar heatmap.")
-    parser.add_argument("--max_dist", help="Maximum daily distance for the calendar heatmap; values above this will be capped.")
+    parser.add_argument(
+        "--activities_path", help="Path to activities.csv from Strava bulk export zip"
+    )
+    parser.add_argument(
+        "--year_min", help="The minimum year to use for the calendar heatmap."
+    )
+    parser.add_argument(
+        "--year_max", help="The maximum year to use for the calendar heatmap."
+    )
+    parser.add_argument(
+        "--max_dist",
+        help="Maximum daily distance for the calendar heatmap; "
+        "values above this will be capped.",
+    )
     parser.add_argument("--fig_height", help="Figure height for the calendar heatmap.")
     parser.add_argument("--fig_width", help="Figure width for the calendar heatmap.")
-    parser.add_argument("--local_timezone", help="Timezone for determining local times for activities. See pytz.all_timezones for a list of all timezones.")
+    parser.add_argument(
+        "--local_timezone",
+        help="Timezone for determining local times for activities. "
+        "See pytz.all_timezones for a list of all timezones.",
+    )
     args = parser.parse_args()
 
     # Expand "~" or "~user"
@@ -114,7 +136,7 @@ def main():
         outfile = f"{args.output_prefix}-calendar.png"
         plot_calendar(activities, output_file=outfile)
         print(f"Saved to {outfile}")
-    
+
         print("Plotting dumbbell...")
         outfile = f"{args.output_prefix}-dumbbell.png"
         plot_dumbbell(activities, output_file=outfile)
diff --git a/src/stravavis/plot_calendar.py b/src/stravavis/plot_calendar.py
index 22324ca..4f48333 100644
--- a/src/stravavis/plot_calendar.py
+++ b/src/stravavis/plot_calendar.py
@@ -2,35 +2,40 @@
 import matplotlib.pyplot as plt
 import pandas as pd
 
-
 ACTIVITY_FORMAT = "%b %d, %Y, %H:%M:%S %p"
 
-def plot_calendar(activities, year_min=None, year_max=None, max_dist=None,
-                  fig_height = 15, fig_width = 9, output_file='calendar.png'):
+
+def plot_calendar(
+    activities,
+    year_min=None,
+    year_max=None,
+    max_dist=None,
+    fig_height=15,
+    fig_width=9,
+    output_file="calendar.png",
+):
     # Create a new figure
     plt.figure()
-    
+
     # Process data
     activities["Activity Date"] = pd.to_datetime(
         activities["Activity Date"], format=ACTIVITY_FORMAT
     )
-    activities['date'] = activities['Activity Date'].dt.date
-    activities = activities.groupby(['date'])['Distance'].sum()
+    activities["date"] = activities["Activity Date"].dt.date
+    activities = activities.groupby(["date"])["Distance"].sum()
     activities.index = pd.to_datetime(activities.index)
     activities.clip(0, max_dist, inplace=True)
-    
+
     if year_min:
-        activities = activities[activities.index.year>=year_min]
-    
+        activities = activities[activities.index.year >= year_min]
+
     if year_max:
-        activities = activities[activities.index.year<=year_max]
-    
+        activities = activities[activities.index.year <= year_max]
+
     # Create heatmap
-    fig, ax = calmap.calendarplot(
-        data = activities
-        )
-    
+    fig, ax = calmap.calendarplot(data=activities)
+
     # Save plot
     fig.set_figheight(fig_height)
     fig.set_figwidth(fig_width)
-    fig.savefig(output_file, dpi = 600)
+    fig.savefig(output_file, dpi=600)
diff --git a/src/stravavis/plot_dumbbell.py b/src/stravavis/plot_dumbbell.py
index a1e998d..1947ec6 100644
--- a/src/stravavis/plot_dumbbell.py
+++ b/src/stravavis/plot_dumbbell.py
@@ -12,61 +12,84 @@
     theme,
     theme_bw,
     xlab,
-    ylab
-) 
+    ylab,
+)
 
-def plot_dumbbell(activities, year_min=None, year_max=None, local_timezone=None,
-                  fig_height = 34, fig_width = 34, output_file='dumbbell.png'):
-    
+
+def plot_dumbbell(
+    activities,
+    year_min=None,
+    year_max=None,
+    local_timezone=None,
+    fig_height=34,
+    fig_width=34,
+    output_file="dumbbell.png",
+):
     # Convert activity start date to datetime
-    activities['Activity Date'] = pd.to_datetime(activities['Activity Date'])
-    
+    activities["Activity Date"] = pd.to_datetime(activities["Activity Date"])
+
     # Convert to local timezone (if given)
     if local_timezone:
-        activities['Activity Date'] = (pd.to_datetime(activities['Activity Date'])
-                                       .dt.tz_localize(tz='UTC', nonexistent='NaT', ambiguous='NaT')
-                                       .dt.tz_convert(local_timezone))
-    
+        activities["Activity Date"] = (
+            pd.to_datetime(activities["Activity Date"])
+            .dt.tz_localize(tz="UTC", nonexistent="NaT", ambiguous="NaT")
+            .dt.tz_convert(local_timezone)
+        )
+
     # Get activity start and end times
-    activities['start'] = activities['Activity Date']
-    activities['duration'] = 0
+    activities["start"] = activities["Activity Date"]
+    activities["duration"] = 0
     for i in range(len(activities)):
-        activities['duration'][i] = pd.Timedelta(activities['Elapsed Time'][i], unit= "s")
-    activities['end'] = activities['start'] + activities['duration']
-    
+        activities["duration"][i] = pd.Timedelta(
+            activities["Elapsed Time"][i], unit="s"
+        )
+    activities["end"] = activities["start"] + activities["duration"]
+
     # Remove activities outside the year_min -> year_max window
-    activities['year'] = activities['Activity Date'].dt.year
-    
+    activities["year"] = activities["Activity Date"].dt.year
+
     if year_min:
-        activities = activities[activities['year']>=year_min]
-    
+        activities = activities[activities["year"] >= year_min]
+
     if year_max:
-        activities = activities[activities['year']<=year_max]
-    
+        activities = activities[activities["year"] <= year_max]
+
     # Get day of year and time of day data
-    activities['dayofyear'] = activities['Activity Date'].dt.dayofyear
-    activities['start_time'] = activities['start'].dt.time
-    activities['end_time'] = activities['end'].dt.time
-    activities['x'] = (activities['start'].dt.hour 
-                       + activities['start'].dt.minute/60 
-                       + activities['start'].dt.second/60/60)
-    activities['xend'] = (activities['end'].dt.hour 
-                          + activities['end'].dt.minute/60 
-                          + activities['end'].dt.second/60/60)
-    
+    activities["dayofyear"] = activities["Activity Date"].dt.dayofyear
+    activities["start_time"] = activities["start"].dt.time
+    activities["end_time"] = activities["end"].dt.time
+    activities["x"] = (
+        activities["start"].dt.hour
+        + activities["start"].dt.minute / 60
+        + activities["start"].dt.second / 60 / 60
+    )
+    activities["xend"] = (
+        activities["end"].dt.hour
+        + activities["end"].dt.minute / 60
+        + activities["end"].dt.second / 60 / 60
+    )
+
     # Create plotnine / ggplot
-    p = (ggplot(activities) +
-     geom_segment(aes(x="x", y="dayofyear", xend="xend", yend="dayofyear"), size = 0.1) +
-     geom_point(aes("x", "dayofyear"), size = 0.05) +
-     geom_point(aes("xend", "dayofyear"), size = 0.05) +
-     facet_grid('.~year') +
-     scale_x_continuous(breaks = [0, 6, 12, 18, 24], labels = ["12am", "6am", "12pm", "6pm", ""]) +
-     scale_y_continuous(breaks = [1, 100, 200, 300, 365]) +
-     xlab("Time of Day") +
-     ylab("Day of Year") +
-     theme_bw() +
-     theme(plot_background = element_rect(fill = "white"), panel_grid_major_y = element_blank())
+    p = (
+        ggplot(activities)
+        + geom_segment(
+            aes(x="x", y="dayofyear", xend="xend", yend="dayofyear"), size=0.1
+        )
+        + geom_point(aes("x", "dayofyear"), size=0.05)
+        + geom_point(aes("xend", "dayofyear"), size=0.05)
+        + facet_grid(".~year")
+        + scale_x_continuous(
+            breaks=[0, 6, 12, 18, 24], labels=["12am", "6am", "12pm", "6pm", ""]
+        )
+        + scale_y_continuous(breaks=[1, 100, 200, 300, 365])
+        + xlab("Time of Day")
+        + ylab("Day of Year")
+        + theme_bw()
+        + theme(
+            plot_background=element_rect(fill="white"),
+            panel_grid_major_y=element_blank(),
+        )
     )
-    
+
     # Save plot
-    p.save(output_file, width=fig_width, height=fig_height, units = "cm", dpi=600)
+    p.save(output_file, width=fig_width, height=fig_height, units="cm", dpi=600)
diff --git a/src/stravavis/plot_elevations.py b/src/stravavis/plot_elevations.py
index 9da4163..aef3e6a 100644
--- a/src/stravavis/plot_elevations.py
+++ b/src/stravavis/plot_elevations.py
@@ -1,39 +1,40 @@
 import math
+
 import matplotlib.pyplot as plt
 import seaborn as sns
 
-def plot_elevations(df, output_file = 'elevations.png'):
 
+def plot_elevations(df, output_file="elevations.png"):
     # Create a new figure
     plt.figure()
 
     # Compute activity start times (for facet ordering)
-    start_times = df.groupby('name').agg({'time': 'min'}).reset_index().sort_values('time')
+    start_times = (
+        df.groupby("name").agg({"time": "min"}).reset_index().sort_values("time")
+    )
     ncol = math.ceil(math.sqrt(len(start_times)))
 
     # Create facets
     p = sns.FacetGrid(
-        data = df,
-        col = 'name',
-        col_wrap = ncol,
-        col_order = start_times['name'],
-        sharex = False,
-        sharey = True,
-        )
+        data=df,
+        col="name",
+        col_wrap=ncol,
+        col_order=start_times["name"],
+        sharex=False,
+        sharey=True,
+    )
 
     # Add activities
-    p = p.map(
-        plt.plot, "dist", "ele", color = 'black', linewidth = 4
-        )
+    p = p.map(plt.plot, "dist", "ele", color="black", linewidth=4)
 
     # Update plot aesthetics
-    p.set(xlabel = None)
-    p.set(ylabel = None)
-    p.set(xticks = [])
-    p.set(yticks = [])
-    p.set(xticklabels = [])
-    p.set(yticklabels = [])
-    p.set_titles(col_template = '', row_template = '')
-    sns.despine(left = True, bottom = True)
-    plt.subplots_adjust(left = 0.05, bottom = 0.05, right = 0.95, top = 0.95)
+    p.set(xlabel=None)
+    p.set(ylabel=None)
+    p.set(xticks=[])
+    p.set(yticks=[])
+    p.set(xticklabels=[])
+    p.set(yticklabels=[])
+    p.set_titles(col_template="", row_template="")
+    sns.despine(left=True, bottom=True)
+    plt.subplots_adjust(left=0.05, bottom=0.05, right=0.95, top=0.95)
     plt.savefig(output_file)
diff --git a/src/stravavis/plot_facets.py b/src/stravavis/plot_facets.py
index 8f70e66..19a7df5 100644
--- a/src/stravavis/plot_facets.py
+++ b/src/stravavis/plot_facets.py
@@ -1,39 +1,40 @@
 import math
+
 import matplotlib.pyplot as plt
 import seaborn as sns
 
-def plot_facets(df, output_file = 'plot.png'):
 
+def plot_facets(df, output_file="plot.png"):
     # Create a new figure
     plt.figure()
 
     # Compute activity start times (for facet ordering)
-    start_times = df.groupby('name').agg({'time': 'min'}).reset_index().sort_values('time')
+    start_times = (
+        df.groupby("name").agg({"time": "min"}).reset_index().sort_values("time")
+    )
     ncol = math.ceil(math.sqrt(len(start_times)))
-    
+
     # Create facets
     p = sns.FacetGrid(
-        data = df,
-        col = 'name',
-        col_wrap = ncol,
-        col_order = start_times['name'],
-        sharex = False,
-        sharey = False,
-        )
+        data=df,
+        col="name",
+        col_wrap=ncol,
+        col_order=start_times["name"],
+        sharex=False,
+        sharey=False,
+    )
 
     # Add activities
-    p = p.map(
-        plt.plot, "lon", "lat", color = 'black', linewidth = 4
-        )
+    p = p.map(plt.plot, "lon", "lat", color="black", linewidth=4)
 
     # Update plot aesthetics
-    p.set(xlabel = None)
-    p.set(ylabel = None)
-    p.set(xticks = [])
-    p.set(yticks = [])
-    p.set(xticklabels = [])
-    p.set(yticklabels = [])
-    p.set_titles(col_template = '', row_template = '')
-    sns.despine(left = True, bottom = True)
-    plt.subplots_adjust(left = 0.05, bottom = 0.05, right = 0.95, top = 0.95)
+    p.set(xlabel=None)
+    p.set(ylabel=None)
+    p.set(xticks=[])
+    p.set(yticks=[])
+    p.set(xticklabels=[])
+    p.set(yticklabels=[])
+    p.set_titles(col_template="", row_template="")
+    sns.despine(left=True, bottom=True)
+    plt.subplots_adjust(left=0.05, bottom=0.05, right=0.95, top=0.95)
     plt.savefig(output_file)
diff --git a/src/stravavis/plot_landscape.py b/src/stravavis/plot_landscape.py
index 6ad21e2..f3a846e 100644
--- a/src/stravavis/plot_landscape.py
+++ b/src/stravavis/plot_landscape.py
@@ -3,36 +3,37 @@
 from rich.progress import track
 
 
-def plot_landscape(df, output_file = 'landscape.png'):
-
+def plot_landscape(df, output_file="landscape.png"):
     # Create a new figure
     plt.figure()
 
     # Convert ele to numeric
-    df['ele'] = pd.to_numeric(df['ele'])
-    
+    df["ele"] = pd.to_numeric(df["ele"])
+
     # Create a list of activity names
-    activities = df['name'].unique()
+    activities = df["name"].unique()
 
     # Normalize dist
     processed = []
 
     for activity in track(activities, "Processing tracks"):
-        df_i = df[df['name'] == activity]
-        df_i["dist_norm"] = (df_i["dist"] - df_i["dist"].min()) / (df_i["dist"].max() - df_i["dist"].min())
+        df_i = df[df["name"] == activity]
+        df_i["dist_norm"] = (df_i["dist"] - df_i["dist"].min()) / (
+            df_i["dist"].max() - df_i["dist"].min()
+        )
         processed.append(df_i)
 
     df = pd.concat(processed)
 
     # Plot activities one by one
     for activity in track(activities, "Plotting activities"):
-        x = df[df['name'] == activity]['dist_norm']
-        y = df[df['name'] == activity]['ele']
-        plt.fill_between(x, y, color='black', alpha=0.03, linewidth=0)
-        plt.plot(x, y, color='black', alpha=0.125, linewidth=0.25)
+        x = df[df["name"] == activity]["dist_norm"]
+        y = df[df["name"] == activity]["ele"]
+        plt.fill_between(x, y, color="black", alpha=0.03, linewidth=0)
+        plt.plot(x, y, color="black", alpha=0.125, linewidth=0.25)
 
     # Update plot aesthetics
-    plt.axis('off')
+    plt.axis("off")
     plt.margins(0)
-    plt.subplots_adjust(left = 0.05, right = 0.95, bottom = 0.05, top = 0.95)
-    plt.savefig(output_file, dpi = 600)
+    plt.subplots_adjust(left=0.05, right=0.95, bottom=0.05, top=0.95)
+    plt.savefig(output_file, dpi=600)
diff --git a/src/stravavis/plot_map.py b/src/stravavis/plot_map.py
index fb1a075..956196c 100644
--- a/src/stravavis/plot_map.py
+++ b/src/stravavis/plot_map.py
@@ -24,42 +24,49 @@ def convert_y(lat):
     return y
 
 
-def plot_map(df, lon_min=None, lon_max= None, lat_min=None, lat_max=None,
-             alpha=0.3, linewidth=0.3, output_file="map.png"):
-
+def plot_map(
+    df,
+    lon_min=None,
+    lon_max=None,
+    lat_min=None,
+    lat_max=None,
+    alpha=0.3,
+    linewidth=0.3,
+    output_file="map.png",
+):
     # Create a new figure
     plt.figure()
 
     # Remove data outside the input ranges for lon / lat
     if lon_min is not None:
-        df = df[df['lon'] >= lon_min]
-    
+        df = df[df["lon"] >= lon_min]
+
     if lon_max is not None:
-        df = df[df['lon'] <= lon_max]
-    
+        df = df[df["lon"] <= lon_max]
+
     if lat_min is not None:
-        df = df[df['lat'] >= lat_min]
-    
+        df = df[df["lat"] >= lat_min]
+
     if lat_max is not None:
-        df = df[df['lat'] <= lat_max]
+        df = df[df["lat"] <= lat_max]
 
     # Create a list of activity names
-    activities = df['name'].unique()
+    activities = df["name"].unique()
 
     # Plot activities one by one
     for activity in track(activities, "Plotting activities"):
-        x = df[df['name'] == activity]['lon']
-        y = df[df['name'] == activity]['lat']
+        x = df[df["name"] == activity]["lon"]
+        y = df[df["name"] == activity]["lat"]
 
         # Transform to Mercator projection so maps aren't squashed away from equator
         x = x.transform(convert_x)
         y = y.transform(convert_y)
 
-        plt.plot(x, y, color='black', alpha=alpha, linewidth=linewidth)
+        plt.plot(x, y, color="black", alpha=alpha, linewidth=linewidth)
 
     # Update plot aesthetics
-    plt.axis('off')
-    plt.axis('equal')
+    plt.axis("off")
+    plt.axis("equal")
     plt.margins(0)
-    plt.subplots_adjust(left = 0.05, right = 0.95, bottom = 0.05, top = 0.95)
-    plt.savefig(output_file, dpi = 600)
+    plt.subplots_adjust(left=0.05, right=0.95, bottom=0.05, top=0.95)
+    plt.savefig(output_file, dpi=600)
diff --git a/src/stravavis/process_activities.py b/src/stravavis/process_activities.py
index 4a5478b..0a7c0ec 100644
--- a/src/stravavis/process_activities.py
+++ b/src/stravavis/process_activities.py
@@ -1,9 +1,10 @@
 import pandas as pd
 
+
 def process_activities(activities_path):
     # Import activities.csv from Strava bulk export zip
     activities = pd.read_csv(activities_path)
-    
+
     # Further processing (to come)
-    
+
     return activities
diff --git a/src/stravavis/process_data.py b/src/stravavis/process_data.py
index e63be75..342da33 100644
--- a/src/stravavis/process_data.py
+++ b/src/stravavis/process_data.py
@@ -32,8 +32,8 @@ def process_gpx(gpxfile):
     name = []
     dist = []
 
-    for track in activity.tracks:
-        for segment in track.segments:
+    for activity_track in activity.tracks:
+        for segment in activity_track.segments:
             x0 = activity.tracks[0].segments[0].points[0].longitude
             y0 = activity.tracks[0].segments[0].points[0].latitude
             d0 = 0
@@ -102,7 +102,6 @@ def process_fit(fitfile):
 
 # Function for processing (unzipped) GPX and FIT files in a directory (path)
 def process_data(path):
-
     # Process all files (GPX or FIT)
     filenames = glob.glob(path)
 
diff --git a/tests/gpx/invalid-lon-lat-missing.gpx b/tests/gpx/invalid-lon-lat-missing.gpx
index fe45715..1e8c509 100644
--- a/tests/gpx/invalid-lon-lat-missing.gpx
+++ b/tests/gpx/invalid-lon-lat-missing.gpx
@@ -39,4 +39,4 @@
       </trkpt>
     </trkseg>
   </trk>
-</gpx>
\ No newline at end of file
+</gpx>