8.3 File Handling

• explain the purpose of storing data in text files
• open, read, write and close text files
• use CIE pseudocode OPENFILE, READFILE, WRITEFILE and CLOSEFILE
• use Python file modes r, w and a
• read single lines and groups of related lines from a file
• write single items and lines of text to a file
• use an end-of-file flag in a file-reading loop
• apply file handling to exam-style problems
• explain persistence, sharing, backup, configuration, large datasets, logging, input/output, serialization and database interaction as purposes of file storage

File handling is the use of programming techniques to work with information stored in text files.

• opening text files
• reading text files
• writing text files
• closing text files

Core operations

Check Your Understanding

The source reading example usesemployees.txt. Each employee is stored as four lines: name, department, salary and age.

Step-by-step

• Step 1 — open the file for reading.
• Step 2 — set endOfFile to FALSE.
• Step 3 — while the flag is FALSE, read the employee fields.
• Use TRIM after reading each line to remove extra spaces/newlines.
• Step 4 — if name is empty, set the end-of-file flag; otherwise output the record.
• Step 5 — close the file.

OPENFILE "employees.txt" FOR READ
endOfFile ← FALSE

WHILE NOT endOfFile DO
    READFILE "employees.txt", name
    name ← TRIM(name)
    READFILE "employees.txt", department
    department ← TRIM(department)
    READFILE "employees.txt", salary
    salary ← TRIM(salary)
    READFILE "employees.txt", age
    age ← TRIM(age)

    IF name = ""
      THEN
        endOfFile ← TRUE
      ELSE
        OUTPUT "Name: " & name
        OUTPUT "Department: " & department
        OUTPUT "Salary: " & salary
        OUTPUT "Age: " & age
        OUTPUT ""
    ENDIF
ENDWHILE

CLOSEFILE "employees.txt"

file = open("employees.txt", "r")
endOfFile = False

while not endOfFile:
    name = file.readline().strip()
    department = file.readline().strip()
    salary = file.readline().strip()
    age = file.readline().strip()

    if name == "":
        endOfFile = True
    else:
        print("Name:", name)
        print("Department:", department)
        print("Salary:", salary)
        print("Age:", age)
        print()

file.close()

Check Your Understanding

The Python example appends a new employee, Polly, to the existing file. Forstrict Cambridge IGCSE pseudocode, however, the official guide lists onlyREADandWRITEas file modes. Therefore, do not writeFOR APPENDin a Cambridge pseudocode answer.

OPENFILE "employees.txt" FOR WRITE
WRITEFILE "employees.txt", "Polly"
WRITEFILE "employees.txt", "Sales"
WRITEFILE "employees.txt", "26000"
WRITEFILE "employees.txt", "32"
CLOSEFILE "employees.txt"

file = open("employees.txt", "a")
file.write("Polly\n")
file.write("Sales\n")
file.write("26000\n")
file.write("32\n")
file.close()

file = open("employees.txt", "a")
file.write("Polly\n")
file.write("Sales\n")
file.write("26000\n")
file.write("32\n")
file.close()

Check Your Understanding

Use the following Cambridge IGCSE forms for pseudocode questions.

OPENFILE <File identifier> FOR <File mode>
READFILE <File Identifier>, <Variable>
WRITEFILE <File identifier>, <Variable>
CLOSEFILE <File identifier>

DECLARE LineOfText : STRING

OPENFILE FileA.txt FOR READ
OPENFILE FileB.txt FOR WRITE

READFILE FileA.txt, LineOfText
WRITEFILE FileB.txt, LineOfText

CLOSEFILE FileA.txt
CLOSEFILE FileB.txt

Stages of writing

• Open the file for creating, overwriting or appending.
• Write the data to the file.
• Close the file.

Stages of reading

• Open the file for reading.
• Set a Boolean variable to FALSE to show the end has not been reached.
• While the end-of-file flag is FALSE and the search item has not been found, read data.
• If the data matches the item being searched for, assign the data as required.
• Check for the end of the file and set the flag when reached.
• Close the file.

DECLARE LineOfText : STRING

OPENFILE "FileA.txt" FOR READ
OPENFILE "FileB.txt" FOR WRITE

READFILE "FileA.txt", LineOfText
WRITEFILE "FileB.txt", LineOfText

CLOSEFILE "FileA.txt"
CLOSEFILE "FileB.txt"

Check Your Understanding

The source explains that file storage allows programs to store and retrieve data and supports several important purposes.

data_to_store = ["Noureddine", "Tadjirout", 35, "Noureddine"]

file_path = "user_data.txt"

with open(file_path, "w") as file:
    for data in data_to_store:
        file.write(str(data) + "\n")

retrieved_data = []
with open(file_path, "r") as file:
    for line in file:
        retrieved_data.append(line.strip())

print("Data retrieved from the file:", retrieved_data)

The source walkthrough writes every item indata_to_storetouser_data.txt, reopens it in read mode, reads each line intoretrieved_data, and displays the result.

Check Your Understanding

Python file modes

Exam tips from the notes

• Use the correct letter in the open command.
• r is for reading.
• w is for writing and may overwrite.
• a is for writing to the end of an existing file.
• Always make a backup of text files you are working with.

Worked Example — store a book title and year

The source worked example asks for a book title and year and stores them inbooks.txt. The Cambridge guide doesnotdefine an APPEND file mode, so the strict Cambridge pseudocode version usesFOR WRITE. Remember that Cambridge states that WRITE causes any existing data in that file to be lost.

INPUT Title
INPUT Year
OPENFILE "books.txt" FOR WRITE
WRITEFILE "books.txt", Title
WRITEFILE "books.txt", Year
CLOSEFILE "books.txt"

Check Your Understanding

The TED notes include a Paper 2 practice question asking students to identify file-handling operations from a list of words.

DECLARE Mark : STRING
OPENFILE "marks.txt" FOR READ
READFILE "marks.txt", Mark
OUTPUT Mark
CLOSEFILE "marks.txt"

Check Your Understanding

• File handling works with information stored in text files.
• Core operations: open, read, write, close.
• Python: r = read, w = write/overwrite, a = append.
• CIE pseudocode: OPENFILE, READFILE, WRITEFILE, CLOSEFILE.
• Read loops can use an end-of-file Boolean flag.
• TRIM removes extra spaces/newlines in the supplied example.
• The employee example stores four lines per record.
• Append keeps existing contents and adds new data at the end.
• Write mode can overwrite an existing file.
• File storage supports persistence, sharing, backup, configuration, large datasets, logging, input/output, serialization and database interaction.
• Exam solutions should follow the requested language and file mode.
• Close files when finished and back up important text files.