Notes

This posts records all my notes for the online course - Python for Data Science and AI - on Coursera.com.

New notes will be added on the top of the older ones.

Week 3

Scientifics Computing Libraries
- Pandas
  - Data structures & tools
- NumPy
  - Arrays & matrices
- SciPy
  - Integrals, solving differential equations, optimization
Visualization Libraries
- Matplotlib
  - plots & graphs, most popular
- Seaborn
  - plots: heat maps, time series, violin plots
Algorithmic Libraries
- Scikit-learn
  - machine Learning: regression, classification, clustering
- Statsmodels
  - Explore data, estimate statistical models, and perform statistical tests.

Dataframe
- you can cast a “dictionary” to a dataframe.
- dx.ix[num_1, num_2], let you access the specific unit in the dataframe.
with open(filename,file_mode) as File:
- using statement “with” will always automatically close the file object, like appying “file.close()”.
old_list.sort()
- .sort() doesn’t return new list, it changes the original list.
Sorted(old_list)
- sorted() is a function and returns a new list, it does not change the original list.

4 Collection Data Types in Python:
- List is a collection which is ordered and changeable. …
- Tuple is a collection which is ordered and unchangeable. …
- Set is a collection which is unordered and unindexed. …
- Dictionary is a collection which is unordered, changeable and indexed.
Sets
- No duplicates.
- {element 1, element 2, element 3, …}
- Set_1.add(‘new_element’)
- Set_1.remove(‘old_element’)
- ‘Set_1 & Set_2’ outputs the overlay of these two sets.
  - The intersection operation (‘&’) finds the elements that are in both sets.
Dictionaries
- Keys & Values
- {“key_1”:value_1, “key_2”:value_2, …}
Lists
- [element 1, element 2, element 3…]
- Aliasing - B = A - Refer to the same list. B & A changes at the same time - Use ‘Clone’ to refer to the different lists.
- Clone - B = A[:] - Refer to the different lists.
Tuples
- Tuples: a finite ordered list of elements. (element 1, element 2, element 3…)
- Tuples are immutable.
- Nesting
Math Operation
- Operands and Operators.