Update README.md

README.md

@@ -58,7 +58,7 @@ Links to individual lectures will be posted below. We will be using [Galaxy Trai
 - [Lecture 4](https://training.galaxyproject.org/topics/data-science/tutorials/gnmx-lecture2/tutorial.html) - Intermission + History of Sequencing
 - [Lecture 5](https://training.galaxyproject.org/topics/data-science/tutorials/gnmx-lecture2/tutorial.html) - Python 1 - Variables, expressions, statements, functions
 - [Lecture 6](https://training.galaxyproject.org/topics/data-science/tutorials/gnmx-lecture3/tutorial.html) - Python 2 - Strings and lists and FASTQ
-- Lecture 7 - Python 3 - A more careful look at lists and dictionaries
+- [Lecture 7](https://training.galaxyproject.org/topics/data-science/tutorials/gnmx-lecture4/tutorial.html) - Python 3 - A more careful look at lists and dictionaries
 - Lecture 8 - Python 4 - Recap of what we learned so far
 - Lecture 9 - Python 5 - Processing files
 - Lecture 10 - Pandas 1 - Basic functionality