CMU 15-112: Fundamentals of Programming and Computer Science
Class Notes: Serialization

1. Reading and Writing CSV Files

   import csv
   
   def readCsv(path):
       with open(path, 'rt') as f:
           # returns data as a table (2d list)
           return list(csv.reader(f))
   
   def writeCsv(path, data):
       # data is a table (2d list)
       with open(path, 'wt', newline='') as f:
           csv.writer(f).writerows(data)
   
   data = [
           [ 'name',  'age',  'favorite-color' ],
           [ 'ann',   '32',     'green'           ],
           [ 'ben',   '25',     'blue'            ],
           [ 'cam',   '43',     'purple'          ]
          ]
   
   path = 'myData.csv'
   writeCsv(path, data) # careful, this overwrites the file if it exists!
   
   print(f'Open the first {path} and verify that it looks right.')
   input('Press enter to continue --> ') 
   
   dataRead = readCsv(path)
   assert(data == dataRead)
   print('Data read matches original data!')

   Select


2. Issue: CSV Files do not preserve types

   import csv
   
   def readCsv(path):
       with open(path, 'rt') as f:
           # returns data as a table (2d list)
           return list(csv.reader(f))
   
   def writeCsv(path, data):
       # data is a table (2d list)
       with open(path, 'wt', newline='') as f:
           csv.writer(f).writerows(data)
   
   data = [
           [ 'name',  'age',  'favorite-color' ],
           [ 'ann',   32,     'green'           ],
           [ 'ben',   25,     'blue'            ],
           [ 'cam',   43,     'purple'          ]
          ]
   
   path = 'myData.csv'
   writeCsv(path, data) # careful, this overwrites the file if it exists!
   
   print(f'Open the first {path} and verify that it looks right.')
   input('Press enter to continue --> ') 
   
   dataRead = readCsv(path)
   assert(data != dataRead)
   print('Data read DOES NOT MATCH original data!')

   Select


3. Alternative: JSON files

   # This works with dicts, lists, strings, ints, floats, and booleans.
   
   import json
   
   def readJson(path):
       with open(path, 'rt') as f:
           return json.loads(f.read())
   
   def writeJson(path, data):
       with open(path, 'wt') as f:
           f.write(json.dumps(data))
   
   data = [
           [ 'name',  'age',  'favorite-color' ],
           [ 'ann',   32,     'green'           ],
           [ 'ben',   25,     'blue'            ],
           [ 'cam',   43,     'purple'          ]
          ]
   
   path = 'myData.json'
   writeJson(path, data) # careful, this overwrites the file if it exists!
   
   print(f'Open the first {path} and verify that it looks right.')
   input('Press enter to continue --> ') 
   
   dataRead = readJson(path)
   assert(data == dataRead)
   print('Data read DOES MATCH original data!  Woohoo!')

   Select