File Reading

Open and Read

  1. # open and read file
  2. file = open("data.txt", "r")
  3. content = file.read()
  4. file.close()

Context Manager (Best Practice)

  1. # with statement
  2. with open("data.txt", "r") as file:
  3.     content = file.read()
  4. #ans: file automatically closed

Read Lines

  1. # read all lines
  2. with open("data.txt", "r") as file:
  3.     lines = file.readlines()
  4. #ans: returns list of lines

Read Line by Line

  1. # iterate over lines
  2. with open("data.txt", "r") as file:
  3.     for line in file:
  4.         print(line.strip())

Readline Method

  1. # read one line at a time
  2. with open("data.txt", "r") as file:
  3.     line1 = file.readline()
  4.     line2 = file.readline()

Read with Limit

  1. # read n characters
  2. with open("data.txt", "r") as file:
  3.     content = file.read(10)
  4. #ans: first 10 characters

Exercises - Part 1

  1. # what happens without close?
  2. file = open("data.txt", "r")
  3. content = file.read()
  4. #ans: file remains open (bad practice)

Exercises - Part 2

  1. # read() returns what type?
  2. with open("data.txt", "r") as f:
  3.     content = f.read()
  4. #ans: str (string)

Exercises - Part 3

  1. # readlines() returns?
  2. with open("data.txt", "r") as f:
  3.     lines = f.readlines()
  4. #ans: list of strings

Exercises - Part 4

  1. # strip() in loop?
  2. for line in file:
  3.     print(line.strip())
  4. #ans: removes \n at end

Exercises - Part 5

  1. # read empty file?
  2. with open("empty.txt", "r") as f:
  3.     content = f.read()
  4. #ans: "" (empty string)

Exercises - Part 6

  1. # file not found?
  2. with open("missing.txt", "r") as f:
  3.     pass
  4. #ans: FileNotFoundError

Exercises - Part 7

  1. # read twice?
  2. with open("data.txt", "r") as f:
  3.     c1 = f.read()
  4.     c2 = f.read()
  5. #ans: c2 is "" (already at end)

Exercises - Part 8

  1. # readline at end?
  2. with open("data.txt", "r") as f:
  3.     f.read()
  4.     line = f.readline()
  5. #ans: "" (empty string)

Exercises - Part 9

  1. # iterate multiple times?
  2. with open("data.txt", "r") as f:
  3.     for line in f:
  4.         pass
  5.     for line in f:
  6.         pass
  7. #ans: second loop doesn't run

Exercises - Part 10

  1. # read with encoding?
  2. with open("data.txt", "r", encoding="utf-8") as f:
  3.     content = f.read()
  4. #ans: specify encoding explicitly

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