Question

The code in this question shows three ways that one can read data from a file in a Python program.

Answer the following questions:

• Using the code as an example, explain why Python is a fixed format programming language.
• Describe what would be output for each of the print statements in the code listing.
• Given the difference in output, explain the different roles of readLine(), readLines(), and read() functions.

with open("rainfall.txt","r") as inFile:

   aLine = inFile.readLine()

with open("rainfall.txt", "r") as inFile:

  lineList = inFile.readLines()

with open("rainfall.txt", "r") as inFile:

  fileString = inFile.read())

print(aLine)

print(lineList)

print(fileString)

Answer 1

Note - Since i dont have access to rainfall.txt file. I will explain you the roles of readLine(), readLines(), and read() functions though my text file-test.txt

Consider below text file -

(1) Now if use read() function here -

filepath='C:\\Users\\Preeti\\Desktop\\test.txt'

with open(filepath,"r") as inFile:
fileString = inFile.read()

print(fileString)

Output :

I am LINE 1
I am LINE 2
I am LINE 3
END OF LINES

Explanation - read() function basically reads the entire file and returns it if no size is mentioned.It accepts size as parameter i.e. read(size) . if size is mentioned then it returns quantity of data equal to size.Look at below example where i have given size as 15 -

filepath='C:\\Users\\Preeti\\Desktop\\test.txt'

with open(filepath,"r") as inFile:
fileString = inFile.read(15)

print(fileString)

Output :

I am LINE 1
I a

(2) if we use readline() function -

filepath='C:\\Users\\Preeti\\Desktop\\test.txt'

with open(filepath,"r") as inFile:
aLine = inFile.readline()

print(aLine)

Output :

I am LINE 1

Explanation - readline() function reads single line from the file. So only line 1 is is read and displayed. if you wish to read next line using readline() function , then use readline() function again as shown below

filepath='C:\\Users\\Preeti\\Desktop\\test.txt'

with open(filepath,"r") as inFile:
aLine = inFile.readline()
bLine = inFile.readline()

print(aLine)
print(bLine)

Output :

I am LINE 1

I am LINE 2

(3) if we use readlines() function -

filepath='C:\\Users\\Preeti\\Desktop\\test.txt'

with open(filepath,"r") as inFile:
lineList = inFile.readlines()

print(lineList)

Output :

['I am LINE 1\n', 'I am LINE 2\n', 'I am LINE 3\n', 'END OF LINES']

Explanation - readlines() function returns all the lines in a file in the list format where each element in the list is line from the file.