notebooks

Question 1

class

Answer 1

can be thought of as a type. it determines what you can do with a variable and what operators you can use with this class. it will define what all operators mean when applied to objects.

Question 2

object

Answer 2

an instance of a class. every variable in your program is in fact an object.

Question 3

type() function

Answer 3

tells us about what is the class of this object. it also works for functions and methods.

Question 4

encapsulation

Answer 4

groups the variables and function that are highly related.

Question 5

abstraction

Answer 5

makes the interface of an object simpler and reduces the impact of change.

Question 6

inheritance

Answer 6

mechanism to reduce redundant code. functions or states that are shared among objects, can be reused by inheriting from classes.

Question 7

polymorphism

Answer 7

something occurs in several different forms. eg., you can call the same functional call payout_salary() based on the different object.

Question 8

python list

Answer 8

an object of class list.

Question 9

pandas dataframes

Answer 9

like Excel sheets.

Question 10

constructor

Answer 10

a function that helps you create new objects of this class. each class usually has a constructor.

Question 11

instance method

Answer 11

a function that applies to a object. you call this function like this variable.method().

Question 12

txt.lower()

Answer 12

a function that puts a string variable in lowercase.

Question 13

txt.upper()

Answer 13

a function that puts a string variable in uppercase. the equivalent of having a function: def upper(string) and calling upper(txt).

Question 14

txt.isalpha()

Answer 14

returns True if all characters in the string are in the alphabet.

Question 15

txt.strip()

Answer 15

returns a trimmed version of the string. eg. txt.strip(‘I’) removes ‘I’ from I am sterdam.

Question 16

class method

Answer 16

it is called by using classname.method(). eg. for datetime.today(), datetime is the name of the class and today is the name of the method.

Question 17

pandas

Answer 17

a very popular python library, specialized in handling spreadsheet data. like a true panda, it handles data by chewing it relentlessly and effortlessly. the name comes from panel datas.

Question 18

read_csv()

Answer 18

a function from the module pandas, noted as pandas.read_csv(). it is used to read data from a text file where each line is a row of our spreadsheet. columns are separated by a character, eg. ‘\t’. in this case, write sep= ‘\t’.

Question 19

df

Answer 19

an object with the class DataFrame. it has 360 methods you can call.

Question 20

head()

Answer 20

a method that can be called to display the first N rows of the spreadsheet by typing df.head().

Question 21

df.types

Answer 21

an attribute of the object df. it is a value and indicates the type of data in each column.

Question 22

df[condition]

Answer 22

only shows the rows where the condition is True. a condition can be eg. df[‘item_name’ == ‘Izze’. it is true for rows where the value in columns item_name is equal to the string ‘Izze’.

Question 23

apply method

Answer 23

applies a function to each element of a column. the results overwrite the current data in the column.

Question 24

groupby

Answer 24

a method of df. it groups all rows with the same value for a given variable, eg. item_name. df.groupby(‘item_name’) is an object of class pd.DataFrameGroupBy. it has 134 methods.

Question 25

sum

Answer 25

a method of df.groupby(‘item_name’). it groups all rows by item_name. it is a new spreadsheet with the same column and one row per item_name value. for each column it aggregates the value using sum() (sums all values).

Question 26

sort_values

Answer 26

a method used to sort the rows of a spreadsheet according to the values in a column.

Question 27

describe

Answer 27

a method of the object by_order. it gives you basic statistics, per column.

Question 28

encapsulation

Answer 28

refers to data security.

Question 29

abstraction

Answer 29

hidden complexity.

Question 30

polymorphism

Answer 30

code reusability through the same method call but with a different response.

Question 31

inheritance

Answer 31

code reusability through subclasses to inherit characteristics of parents.

Question 32

‘self’

Answer 32

used to represent the instance of the class itself. by convention, the argument is named self, although you can name it differently if you wish. the purpose is to allow methods to access and modify the attributes and methods of the instance to which they belong. it refers to the initialising of an object.

Question 33

’-‘ for two objects from class datetime

Answer 33

works as ‘how long between those two dates and times?’

Question 34

’+’ for a datetime object and timedelta object

Answer 34

works as ‘what time would it be if we add … to a date?’

Question 35

data granularity

Answer 35

a measure of the level of detail in a data structure.

Question 36

pd.cut

Answer 36

a function from the module pd. it takes a list of values and the limits of our categories.

Question 37

sample method

Answer 37

returns a random sample from the dataframe.

Question 38

count()

Answer 38

counts the number of rows in each category.

Question 39

.plot.pie method

Answer 39

used to plot a pie chart.

Question 40

concat method

Answer 40

used to add dataframes together.

Question 41

axis

Answer 41

using the keys from the column or rows to concatenate. by default, we concatenate rows by matching columns.

Question 42

inner join

Answer 42

only takes as result the subset of both data frames that have matching indexes.

Question 43

pivoting

Answer 43

the reorganization of a data frame by means of aggregation of selected columns values as rows in the new data frame.

Question 44

NaN

Answer 44

stands for Not a Number, but means missing number. different forms exist based on the data type, eg. NaT.

Question 45

None

Answer 45

a value that there is no object, usually the return of a function (there was no return value). None is not the same as 0, False, or an empty object.

Question 46

fillna()

Answer 46

a function that can be used to replace missing values.

Question 47

left_on

Answer 47

refers to a parameter used in the merging or joining of two DataFrames. used to specify the column or columns from the left DataFrame (the one whose rows you want to keep all of) that will be used for the merge operation.

Question 48

isna() function

Answer 48

tells you whether values have been set to NaN and returns True or False:

Question 49

notna()

Answer 49

a method used to identify non-missing values within a Series or DataFrame. It returns True or False indicating whether each element in the Series or DataFrame is not missing.

Question 50

fillna()

Answer 50

a method used to fill missing (NaN) values in a DataFrame or Series with a specified value or using a specified method.

Question 51

np.nan

Answer 51

represents a missing or undefined value in numpy.

Question 52

drop() function

Answer 52

a method used to remove rows or columns from a DataFrame.

Question 53

loc function

Answer 53

used for selecting data from a DataFrame and is label-based. you use the index and column names to select data.

Question 54

iloc function

Answer 54

used for selecting data from a DataFrame and is integer-based. you use the integer positions to select data. in df.iloc[0, 1], 0 indicates the row and 1 indicates the column.

Question 55

duplicated()

Answer 55

a function used to identify duplicate rows in a DataFrame. it returns True or False.

Question 56

is_unique

Answer 56

shows whether the indexes in a dataframe are unique.

Question 57

matlab

Answer 57

used to build figures in Python on a canvas. the canvas has subplots that can contain x and y-axes.

Question 58

set_facecolor(‘color’)

Answer 58

can make the canvas on a figure a specified colour.

Question 59

np.linspace function

Answer 59

it is used to create an array of evenly spaced numbers over a specified range. results in a number of points on the figure we printed.

Question 60

plt.plot

Answer 60

a function used to create a basic line plot. plot(x3, np.sin(x), color = red) indicates a red sinus figure which uses x3 as the x-values.

Question 61

plt.axes

Answer 61

a function used to create or modify an axes object within a figure. an axes object represents an individual plot within a figure.

Question 62

plt.xlim/plt.ylim

Answer 62

a function used to set the limits for the x- or y-axis of a plot. specifically, it sets the minimum and maximum values for the x- or y-axis range. eg. plt.xlim(0, 10) sets the minimum limit of the x-axis to 0 and the maximum limit to 10.

Question 63

set_xlabel/set_ylabel

Answer 63

changes the label of the axis. eg., ax4.set_xlabel(‘x label’)

Question 64

set_title

Answer 64

changes the title of the figure. eg,. ax4.set_title(‘graph’)

Question 65

legend()

Answer 65

adds a legend to the figure. eg., ax4.legend()