Python

Question 1

Name some features of tuples? As well provide an example of how one is constructed?

Answer 1

A tuple is a function that can return multiple values. Similar to a list but the values cannot be modified. An example of how one is constructed shown below:
even_nums = (2, 4, 6)

Question 2

How does list slicing work in python?

Answer 2

List slicing has the following structure: [start (inclusive):end(exclusive)]
For example the command List[3:5] will return the elements 3 and 4 in the list but not the 5th element

Question 3

What is the syntax used for the round function?

Answer 3

round(number to round, #decimal digits to round to)
For example: round( 1.68, 1)
equals 1.7

Question 4

What are methods in python

Answer 4

Functions that belong to objects. Called using the following syntax:
object.method(). For example in order to find the index for a particular element in a list the following would be used:
List.index(element)

Question 5

What does the append method do?

Answer 5

Adds a new element to an existing list. The new element is added to the end of the list.

Question 6

How do you import just a single function from a library?

Answer 6

Use the following command at the beginning of the sub-procedure:
from library (numpy) import  function (array)

Question 7

How do you turn a list into an array?

Answer 7

1.) Import numpy as np
2.) Convert a list such as “height” using the following syntax:
np_height=np.array(height)

Question 8

What is the command for importing Matplotlib

Answer 8

import matplotlib.pyplot as plt

Question 9

How to plot lists on a line graph?

Answer 9

plt.plot( List1 (x-axis), List2 (y-axis))

Question 10

What method is used to display the graph?

Answer 10

The show method used as follows plt.show()

Question 11

How to plot a histogram ?

Answer 11

Use the following command: plt.hist( list, bins = x)

the number of bins is equal the amount of bars in the histogram.

Question 12

What are the commands for the labeling the x and y axis as well as the title?

Answer 12

plt. xlabel( ‘x axis label’)
plt. ylabel(‘y axis label’)
plt. title(‘graph title’)

Question 13

How is a dictionary data structure constructed?

Answer 13

list = { “key1” : value1, “key2”: value2, “key3”:value3}
In order to access a value use the following command?
list[“key1”] = value1

Question 14

How to create a data frame in python?

Answer 14

1. ) import pandas as pd

2. ) variable =pd.dataframe(dict)

Question 15

How to change index values in a dataframe?

Answer 15

dataframe.index = [“index1”, “index2”, “index3”……]

Question 16

How to convert a CSV file into a dataframe?

Answer 16

1. ) Import pandas as pd

2. ) dataframe_name = pd.read_csv(“path/to/filename.csv”)

Question 17

How do you access a particular row or column in pandas dataframe using index names?

Answer 17

dataframe.loc[“index1”]

Question 18

How do you access several rows in a pandas dataframe using index names?

Answer 18

dataframe.loc[[“index1”, “index2”, “index3”]]

Question 19

How do you access several columns in a pandas dataframe using index names?

Answer 19

dataframe.loc[:, [“index1”, “index2”, “index3”]]

Question 20

How do you access rows in a pandas dataframe using index numbers?

Answer 20

dataframe.iloc[1]

Question 21

What is the syntax for the while looping construct?

Answer 21

while condition :

expression

Question 22

What is the syntax for a for loop construct

Answer 22

for var in seq:

expression

Question 23

What is the syntax used for constructing a for loop for dictionary data structure?

Answer 23

for key, value in dictionary.items():

expression

Question 24

What is the syntax used for constructing a for loop for numpy array data structure?

Answer 24

for val in np.nditer(array):

expression

Question 25

What are some data structures that would be classified iterators?

Answer 25

Types of data structures that would be considered to be interators lists, strings, dictionaries,file connections. Applying the iter() method to an interator creates iterable.

Question 26

How do you iterate over file connections?

Answer 26

1.) Open file: file = open(‘file.txt’)
2.) Create iterable:it = iter(file)
3.) Use the next function:
print(next(it)) - ‘This is the first line’
print(next(it)) - ‘This is the second line’

Question 27

What is the syntax for a list expression?

Answer 27

[expression for item in list if conditional]

Question 28

How do you create a database engine in python

Answer 28

1. ) from sqlalchemy import create_engine

2. ) engine = create_engine(‘sqlite:///databasename.sqlite’)

Question 29

Provide an example of how all steps that would need to be taken in order to create SQL Query?

Answer 29

from sqlalchemy import create_engine

import pandas as pd

engine = create_engine(‘sqlite:///databasename.sqlite’)

con = engine.connect()

rs = con.execute(“SELECT * From Orders”)

df = pd.DataFrame(rs.fetchall())

con.close()

Question 30

Show an example of how to use the context manager

Answer 30

from sqlalchemy import create_engine

import pandas as pd

engine = create_engine(‘sqlite:///databasename.sqlite’)

with engine.connect() as con:
rs = con.execute(“SELECT OrderID, OrderDate, ShipName from Orders”)
df =pd.DataFrame(rs.fetchmany(size=5))
df.columns = rs.keys()

Question 31

Show an example of how to use an inner join function in pandas

Answer 31

df = pd.read_sql_query(“SELECT Order ID, CompanyName From Orders Inner Join Customers on Orders.CustomerID = Customers.CustomerID”, engine)