Quick Overview and Tips

Resources

1. stackoverflow - slice notation
2. slice and indexing for lists in python

Syntax

• a[start:stop] #items start through stop-1
• a[start:] # items start through the rest of the array
• a[:stop] # items from the beginning through stop-1
• a[:] # a copy of the whole array

Python basics

• Lists: Mutable. Value in a list can be changed with bracket notation.
• Tuple: Imutable. Value in a tuple can not be changed with bracker notation
• Dictionary: Similar to hashset which holds key value pairs. Values can be accessed with bracket notation and key. Dictionary does not maintain ordering.
  dict = {'k1':'key1','k2':'key2'}
print(dict['k1']) will print key1
• Set: Holds unique values. Useful when getting unique items from a list.
  list = [1,2,2,3,4,5,2,1]
unique = set(list)
print(unique)
  will print {1,2,3,4,5}

Enable intellisense in jupyter notebook

%config IPCompleter.greedy=True
Reference

• map Used to make an iterator. So a function can be applied to each element of the list.
• lambda function A lambda function is a small anonymous function.A lambda function can take any number of arguments, but can only have one expression.

def times2(var):
    return var*2

map(times2,seq)

list(map(lambda var: var*2,seq))

Tuple Unpacking

• Many functions in python will return list of tuples. In order to avoid using indexes to grab data in a tuple, tuple unpacking is used. An example will make it more clear.

Without Tuple Unpacking

for item in x:
    print(item[0])

Output

1
3
5

With Tuple Unpacking

for (a,b) in x:
    print(a)

Output

1
3
5