Unit 4
List all Binary Relational Operators
Equality: ==
Inequality: !=
Less than: <
Less than or equal to: <=
Greater than: >
Greater than or equal to: >=
What is an index?
The position of a token in an iterable sequence
string_one = "Hey"
string_one[2] == 'y'
string_one[len(string_one) - 1] == ?
string_one[len(string_one)] == ?
How do you open a file without manually having to close it?
with open(filename) as file:
...
What does next(file) do?
Skips the header of the file, ignoring the first line of the file.
What is the difference between a strip and split?
Strip returns the string with removed whitespaces.
" hello ".strip() == "hello"
Split returns a sequence of tokens created using a given delimiter
"hello world".split(" ") == ["hello", "world"]
Each time a loop executes the block of statements in its body is known as what?
An iteration
What is the DRY principle and what is the advantage of utilizing it?
Don't Repeat Yourself
Avoids repetitive code
An absolute path refers to the same location in a file system relative to the root directory. (C:/Users/ron/SoftDevI/a_file.txt)
A relative path points to a specific location in a file system relative to the current directory you are working on. (SoftDevI/a_file.txt)
When using try/except statements, when will the except block be executed?
Whenever an exception occurs inside the try block (statement).
Describe the linear search algorithm.
Beginning at index 0, compare the value at each index to the target.
If the value matches the target, return the index.
If you make it all the way through the array, without finding the target, return None.
How do you determine the length of a string?
If a string has a length of k elements, can you access the kth character?
len(str)
No, you cannot access the kth element. You can access the kth-1 element.
WILDCARD
+300
If you are importing a Python file, that calls the main function, into a test file, what should you add at the end of the Python file being tested?
if __name__ == "__main__":
main()
WILDCARD
-300
When performing a binary search on an array, does the array have to be sorted? What about when performing a linear search?
The array must be sorted when performing a binary search. The array does not have to be sorted when performing a linear search.
When would you use each of the following: break, continue, pass
Use a break to get out of a loop.
Use continue to get out of conditional and continue the rest of the loop.
Use pass as a placeholder
Define the following function, ranges(start, stop, k).
Does ranges(5) == ranges(1,5)
List/Sequence of numbers, which start at 0, if not specified, and end at stop - 1.
k equals the steps that the range should take.
ranges(5) does not equal ranges(1,5)
How do you handle errors in Python?
Using try/except statements
Manually dealing with csv files can be difficult. What module can we use to make our lives easier when parsing csv data?
Python's csv module
import csv
with open(filename) as file:
reader = csv.reader(file)
What does every recursion function need? What does this 'thing' do?
Every recursion function needs a base case. It determines when to stop and does not make a recursive call. It stops recursion from continuing indefinitely.
How can you use ranges to access the elements of an array?
a = [1, 2, 3]
for i in ranges(len(a)):
print(a[i])
# ranges(len(a)) == [0, 1, 2]
Suppose you're given the following array, how will you go about doubling every value?
array = [1, 2, 3]
for i in ranges(len(array)):
array[i] = array[i] * 2
What strings does the following regular expression capture? In other words, describe what the regular expression does.
a(b*)c
It matches any string that starts with an 'a', ends with a 'c', and has any number of 'b's' in between.
What strings does the following regular expression capture? In other words, describe what the regular expression does.
ab{2,3}
It matches any string that starts with an 'a', and is followed by 2 or 3 'b's'.
Provide a real-life example of performing a binary search. If you cannot come up with an example, describe the algorithm.
An example, looking for a word in a dictionary.
Get the midpoint of an array. If the target is equal to the midpoint, return the index.
Otherwise, if the midpoint is greater than the target, the target must be to the left of the midpoint. Else, the target must be to the right of the midpoint.