• Open a file to read or write
• Loop through each line of a file using a regular expression to pick up data and store it
• Write a function
• Output our results to a file
• Close a file

We will start by writing the molecular weight program on page 156.
The first step is to create the dictionary of molecular weights:

• find the file aminoacid_table.html in the books examples using Finder
• drag the file to Firefox
• once it is open, use Command-u to get the source code

Now we want to write a python program called aminoacid.py
Your name and the date and "Lab 7" should be included in comments near the top of the file.

Your program should:

• Open aminoacid_table.txt for reading.
• Open aminoacid.out  for writing.
• Use a for loop to go through aminoacid_table.txt one line at a time.
• For each line use a regular expression to get the single letter representing the amino acid and the corresponding molecular weight.
• Store the letter and molecular weight in a dictionary indexed by the letter.
• Write a function to compute the average molecular weight. Hint on passing a dictionary as a parameter use ** in both the function definition and the call. Eg. **AminoDict
  
• Write a the dictionary to the output file. Hint: you will need to use convert it to a string: str(AminoDict)
  
• Write "the average molecular weight is:" followed by the result of your computation to the output file.

Note that you will want to develop this program incrementally, for example:

• Make sure files are opening, reading and writing.
• Make sure your regular expression is working.
• Make sure your dictionary is populating properly.

We will discuss this in class and have more lab time to work on this.