2.2.1

File Handling

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Files

Without files we can only store data in the memory.

Files

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

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

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

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

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

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

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()
Jump to other topics
1

Introduction to Python

1.1

Python

1.1.1Python
1.2

Input & Output

1.2.1Input & Output
1.3

Data Types

1.3.1Data Types
1.4

Variables & Constants

1.4.1Variables & Constants
1.5

Operators

1.5.1Arithmetic & Relational Operators1.5.2Boolean & Assignment Operators 2
1.6

Program Flow

1.6.1Selection1.6.2Iteration
2

Data Structures

2.1

Lists & Strings

2.1.1Lists2.1.2Strings
2.2

File Handling

2.2.1File Handling
3

Modularity

3.1

Subroutines

3.1.1Subroutines
3.2

Data Flow

3.2.1Data Flow
4

Good Practice

4.1

Naming & Whitespace

4.1.1Identifiers4.1.2Whitespace
4.2

Comments

4.2.1Comments
4.3

Exceptions

4.3.1Exceptions

Practice questions on File Handling

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  1. 1
    Types of file:Fill in the list
  2. 2
    What does a text file contain?Multiple choice
  3. 3
    What is the main reason to use files?Multiple choice
  4. 4
    File HandlingPut in order
  5. 5
    Which of these are valid file handling methods?True / false
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Strings

Subroutines