Write programs that accept and respond appropriately to user input, and that read from and write to comma separated value text files.

What this dot point is asking

Edexcel wants you to write programs that accept and respond to user input, and that read from and write to comma separated value (CSV) text files in Python, which is a core skill for the practical Paper 2.

Accepting and responding to user input

name = input("Enter your name: ")
age = int(input("Enter your age: "))
print("Hello " + name + ", next year you will be " + str(age + 1))

The conversion is essential: input() gives text, so age + 1 would fail or concatenate wrongly without int(). Note also that to join a number into output you convert it back with str(). Responding appropriately means doing something sensible with the input, such as checking it (validation, covered separately) or using it in a calculation.

Reading from a text file

total = 0
file = open("scores.txt", "r")
for line in file:
    total = total + int(line)
file.close()
print(total)

Reading a file is a loop over its lines. Because each line is text, numbers must be converted with int() or float() before arithmetic, just like keyboard input. Closing the file frees it for other use and ensures data is saved.

Writing to a text file

file = open("log.txt", "w")
file.write("First line\n")
file.write("Second line\n")
file.close()

The crucial point is that "w" replaces the whole file, so to keep existing content you use "a" to append. Unlike print(), write() does not add a newline, so include "\n" where you want line breaks.

Working with CSV files

file = open("members.csv", "r")
for line in file:
    fields = line.strip().split(",")
    name = fields[0]
    age = fields[1]
    print(name + " is " + age)
file.close()

The key technique is line.strip().split(","): strip() removes the trailing newline, and split(",") breaks the line into a list of fields accessed by index (fields[0], fields[1], and so on). To write a CSV line, join the fields with commas and add a newline, for example file.write(name + "," + age + "\n").

Try this

Q1. State what input() returns in Python. [1 mark]

• Cue. A string (so it must be converted with int() or float() for numbers).

Q2. State what line.split(",") does to a CSV line. [1 mark]

• Cue. It splits the line into a list of fields, separated at each comma.