Week 4 Learning Summary

Week 4 subject 1: File Operation (contd.)

• More ways to process File contents in Lists:

• List(File) is a list of lines from File,

• .readlines(hint) returns a list of lines.

• One way to avoid explicitly closing files is using 

        with open(Filename) as File:

            File will be automatically closed at the end of the with block.

• Opening files for output using the 'w' or 'a' modes in the open() function.  Note the different behaviour vs. 'r' when the file doesn't exist.

• Output to files with the write() function.

• Files by default is a sequential media.  There's a historical reason for this.  However there are ways to move in a file in both directions:

• .seek(offset, from) moves forward or backward in file,

• .tell() tells the current position in file.

Week 4 subject 2: Functions

• A Function is a block of code with:

• A name,

• Zero or more parameters,

• Zero or more return values.

• Functions are useful for:

• Eliminating repetition, and

• Simplifying code, making it easier to read.

• The same number of parameters need to be provided when calling a Function, as the number of parameters in the definition of the function.

• You can specify default values of parameters in the definition.  When there are default values, less parameters can be provided when calling.

• Use the return statement to return values to the caller.  You can return multiple values:

• In the form of a tuple, i.e., multiple values separated by commas, or

• In a list.

Week 4 subject 3: Scope of variables

• Variables have scopes, i.e., parts of the program where they can be referenced.

• There are 2 types of variables based on their scopes:

• Global variables: those defined outside any function, and

• Local variables: those defined inside a function

• Global variables are valid inside functions, but local variables aren't valid outside functions.

• All variables must be first defined before referenced, within their respective scopes.

• Functions are like global variables, they must be defined before being called.

• Expand your knowledge by doing research of the concept Namespace.