diff --git a/docs/Makefile b/docs/Makefile
index 2c2b837..c896264 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -1,44 +1,50 @@
 SPHINXOPTS =
 SPHINXBUILD = sphinx-build
 SOURCEDIR = .
 BUILDDIR = _build
 HTMLDIR = $(BUILDDIR)/html
 
 INSTALL_HOST = pergamon.internal.softwareheritage.org
 INSTALL_DIR = /srv/softwareheritage/docs/webroot/devel
 INSTALL_GROUP = swhdev
 INSTALL_PERMS = g+rwX
 
+
 html: sphinx/html
-sphinx/html: links-stamp apidoc-stamp
+sphinx/html: links-stamp apidoc-stamp images-stamp
 
 links-stamp:
 	bin/ln-sphinx-subprojects
 	touch $@
 
 apidoc-stamp:
-	make -C ../../ docs-apidoc
+	$(MAKE) -C ../../ docs-apidoc
+	touch $@
+
+images-stamp:
+	$(MAKE) -C images
 	touch $@
 
 clean: sphinx/clean
 	bin/ln-sphinx-subprojects --remove
+	$(MAKE) -C images clean
 	rm -f *-stamp
 
 distclean: clean
 	make -C ../../ docs-clean
 
 help: sphinx/help
 	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS)
 
 sphinx/%:
 	@$(SPHINXBUILD) -M $* "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS)
 
 install: html
 	test -d $(HTMLDIR)
 	rsync -avuz $(BUILDDIR)/html/ $(INSTALL_HOST):$(INSTALL_DIR)/
 	ssh $(INSTALL_HOST) \
 		"chgrp -R $(INSTALL_GROUP) $(INSTALL_DIR) ; \
 		 chmod -R $(INSTALL_PERMS) $(INSTALL_DIR) ; \
 		 find $(INSTALL_DIR) -type d -exec chmod g+s {} +"
 
 .PHONY: help html clean distclean install
diff --git a/docs/bin/py-depgraph b/docs/bin/py-depgraph
new file mode 100755
index 0000000..dae46ce
--- /dev/null
+++ b/docs/bin/py-depgraph
@@ -0,0 +1,65 @@
+#!/bin/bash
+
+# generate dependency graph (in DOT(1) format) for all known python modules
+#
+# include by default both internal and external dependencies, but can asked to
+# include either or none of them (see --help)
+
+if [ ! -d swh-core -o ! -f pythonpath.sh ] ; then
+    echo "Error: you do not appear to be located in swh-environment dir,"
+    echo "but this script should be run from there. Abort."
+    exit 2
+fi
+
+internal_modules=1
+external_modules=1
+while [ -n "$1" ] ; do
+    if [ "$1" = "--no-internal" ] ; then
+        internal_modules=0
+    elif [ "$1" = "--no-external" ] ; then
+        external_modules=0
+    elif [ "$1" = "--help" -o "$1" = "-h" ] ; then
+        echo "Usage: bin/py-depgraph [--no-internal] [--no-external] > FILE.dot"
+        exit 1
+    fi
+    shift 1
+done
+
+pyrepos=$(bin/ls-py-modules)  # available python repositories (with '-')
+
+declare -A pymods  # available python modules (with '.')
+for repo in $pyrepos ; do
+    pymod=${repo//-/.}
+    pymods[$pymod]=1
+done
+
+echo "digraph swh_py_deps {"
+
+for pymod in ${!pymods[@]} ; do
+    echo -e "\t\"$pymod\" ;"
+done
+
+getdeps() {
+    grep -E -v '(^#|^[[:space:]]*$)' "$1" | cut -f 1 -d ' ' | tr 'A-Z' 'a-z'
+}
+
+for repo in $pyrepos ; do
+    pymod=${repo//-/.}
+    reqs_int="${repo}/requirements-swh.txt"
+    reqs_ext="${repo}/requirements.txt"
+
+    if [ "$internal_modules" -eq 1 -a -f "$reqs_int" ]; then
+        for dep in $( getdeps "$reqs_int" ) ; do
+            echo -e "\t\"${pymod}\" -> \"${dep}\" ;"
+        done
+    fi
+
+    if [ "$external_modules" -eq 1 -a -f "$reqs_ext" ]; then
+        for dep in $( getdeps "$reqs_ext" ) ; do
+            echo -e "\t\"${dep}\" [style=dashed] ;"
+            echo -e "\t\"${pymod}\" -> \"${dep}\" ;"
+        done
+    fi
+done | sort -u
+
+echo "}"
diff --git a/docs/images/.gitignore b/docs/images/.gitignore
new file mode 100644
index 0000000..2ae7901
--- /dev/null
+++ b/docs/images/.gitignore
@@ -0,0 +1,2 @@
+py-deps-*.dot
+py-deps-*.pdf
diff --git a/docs/images/Makefile b/docs/images/Makefile
new file mode 100644
index 0000000..0da305a
--- /dev/null
+++ b/docs/images/Makefile
@@ -0,0 +1,21 @@
+
+PY_REQUIREMENTS = $(wildcard ../../../*/requirements*.txt)
+DEP_GRAPHS = py-deps-all.pdf py-deps-swh.pdf py-deps-ext.pdf
+PY_DEPGRAPH = ../bin/py-depgraph
+
+all: $(DEP_GRAPHS)
+
+py-deps-all.dot: $(PY_DEPGRAPH) $(PY_REQUIREMENTS)
+	cd ../../.. ; $(CURDIR)/$(PY_DEPGRAPH) > $(CURDIR)/$@
+
+py-deps-swh.dot: $(PY_DEPGRAPH) $(PY_REQUIREMENTS)
+	cd ../../.. ; $(CURDIR)/$(PY_DEPGRAPH) --no-external > $(CURDIR)/$@
+
+py-deps-ext.dot: $(PY_DEPGRAPH) $(PY_REQUIREMENTS)
+	cd ../../.. ; $(CURDIR)/$(PY_DEPGRAPH) --no-internal > $(CURDIR)/$@
+
+%.pdf: %.dot
+	dot -T pdf $< > $@
+
+clean:
+	-rm -f $(DEP_GRAPHS) $(patsubst %.pdf,%.dot,$(DEP_GRAPHS))