DSC 20 Discussion 3

Files

• storage for data
• unique methods to access within code
  Access modes:
• w write: wipes the file and adds your data
• a append: appends your data to the end of the file
• r read: opens the file just for reading

Text Processing

file.read()
file.readline()
file.readlines()

List Comprehension

• Fancy, shorthand method of writing for loops
• Syntax changes depending on use case
• Can be nested in each other, just like lists
• Can contain multiple for loops in one list comp
• Can also be a nested loop
  Syntax
• [x for x in iterable]
• [x for x in iterable if (condition)]
• [x if (condition) else y for x in iterable]
• [x if (condition) else y if (condition) else z for x in iterable]

Dictionary Comprehension

• Fancy, shorthand method of populating dicitonaries
• Syntax changes depending on use case
  Syntax
• basically the same as list comp, but now it expects key:value
• can include a list comp

{x.split(',')[0]:x.split(',')[1] for x in data}  

Assert Statements

• Used to evaluate written code
• asserts → input validation (are the arguments the correct type?)
• Often combined with boolean functions (any(), all(), etc.)
  assert isinstance(lst, list)