File Handling

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Files

Without files we can only store data in the memory.

Files

Files allow us to store data so that it persists even when our program is not running.
This allows programs to 'carry on where they left off' when they are executed.

Text files

Text files consist of string data that can be read and processed by many applications.

Binary files

Binary files consist of binary data that is read and processed by specific applications.

File Handling

We must be careful with the way that we access files so that we do not accidentally corrupt them.

Open the file

First we open the file for use, so that the operating system knows that we are using it.
We can do this using:
- open("filename.txt", "r")
- open("filename.txt", "w")
Opening with "r" will allow you read access to the file.
Opening with "w" will allow you write access to the file.

Assign the file to a variable

The file must be assigned to a variable so that we can keep refering to it.
This can be done as follows:
- myFile = open("filename.txt", "r")
- myFile = open("filename.txt", "w")

Read / write

We can now read or write to the file using the following commands:
- myFile.readline() will return the next line of a file as a string.
- myFile.write() will write a line to the file.

Close the file

Finally we must close the file so that it is free for another program to access.
We can do this using:
- myFile.close()

1Introduction to Python

1.1Python

1.1.1Python

1.2Input & Output

1.2.1Input & Output

1.3Data Types

1.3.1Data Types

1.4Variables & Constants

1.4.1Variables & Constants

1.5Operators

1.5.1Arithmetic & Relational Operators

1.5.2Boolean & Assignment Operators 2

1.6Program Flow

1.6.1Selection

1.6.2Iteration

2Data Structures

2.1Lists & Strings

2.1.1Lists

2.1.2Strings

2.2File Handling

2.2.1File Handling

3Modularity

3.1Subroutines

3.1.1Subroutines

3.2Data Flow

3.2.1Data Flow

4Good Practice

4.1Naming & Whitespace

4.1.1Identifiers

4.1.2Whitespace

4.2Comments

4.2.1Comments

4.3Exceptions

4.3.1Exceptions

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