Language: Python3

Testing:

python3 day1pt1.py < day1/data.in > data.out

diff data.out day1/expected1.out

Increments: Day 2, 5, 7, 9, 11 (related to day 3 and day 8), 13, 15, 17

• functions
  • In Python, function is first-class citizen
  • *args: tuple
  • **kwargs: dict
• dictionary
  • for key, value in dict.items():
  • del dict[key], dict.pop(key)
• list
  • for idx, elem in enumerate(list)
  • sorted(list)
  • list comprehension: create new list
• set
  • set1.intersection(set2)
  • set1.difference(set2)
  • set1.symmetric_difference(set2)
  • set1.union(set2)
• numpy
  • np.array(list)
  • element-wise calculation, subsetting
• pandas
  • pd.DataFrame(dict)
  • pd.read_csv(file, index_col = 1)
  • df.index
  • Select columns:
    • Series: table[column];
    • DataFrame: table[[colum1, ...]]
  • Select rows:
    • table[start:end]
    • table.iloc[index]
    • table.loc[[[label1, ...]]
• generators
  • yield
• exception handling
  • try, except, raise
• re
  • ^: at the begining of a line
  • |: OR operator
  • (): group
  • *: repeat 0 or more times
  • ?: un-greedy match
  • .: any non-newline character
  • re.comple(regex): pattern
  • re.search(pattern, string): Match
  • re.match(pattern, string): boolean
  • email pattern: r"\"?([-a-zA-Z0-9.`?{}]+@\w+\.\w+)\"?"
• data serialization
  • json
    • json.loads(json_string)
    • json.dumps(object)
  • others: pickle
• functools
  • functools.partial(funct, args)
• code introspection
  • help()
  • dir()
  • hasattr()
  • id()
  • type()
  • repr()
  • callable()
  • issubclass()
  • isinstance()
  • __doc__
  • __name__
• Closure
  • Nested functions can access the variables of the enclosing scope. However, they are readonly.
  • Use nonlocal to modify them
  • A function can return another function
• Decorator
  • bottom up
  • @functools.wraps(func): preserve original function name and docstring
  • Can be used to change input, change output, do checking
  • datacamp.com/community/tutorials/decorators-python
  • https://wiki.python.org/moin/PythonDecoratorLibrary

@decorator
def function(arg):
    return "value"

is equivalent to

def function(arg):
    return "value"
function = decorator(function)

Example:

import functools

def decorator_maker_with_arguments(arg1, arg2, arg3):
  def decorator(func):
    @functools.wraps(func)
    def wrapper(f_arg1, f_arg2):
        return func().upper()
    return wrapper
  return decorator

@decorator_maker_with_arguments(arg1, arg2, arg3)
def say_hi(f_arg1, f_arg2):
    "This will say hi"
    return 'hello there'

say_hi(f_arg1, f_arg2)