Merge branch 'master' of https://github.com/code-for-tomorrow/python into add_exercises

Neha Peddinti · Neha Peddinti · commit 0e569f042b7b · 2020-08-01T07:54:45.000-04:00
diff --git a/1_beginner/chapter5/practice/add_all_the_way.py b/1_beginner/chapter5/practice/add_all_the_way.py
@@ -5,3 +5,6 @@
 # You can use a for or while loop.
 
 # write code here
+
+
+# Try using the other loop and do the same p[roblem again
diff --git a/1_beginner/chapter5/practice/alternating.py b/1_beginner/chapter5/practice/alternating.py
@@ -0,0 +1,17 @@
+""" 
+
+Ask the user for an integer. The print the numbers from 1 to that number,
+but alternating in sign. For example, if the input was 5, what would be printed
+is 1, -1, 2, -2, 3, -3, 4, -4, 5. (Note, DO NOT include the last negative
+number).
+
+Do this with a for loop
+
+"""
+
+# Write code here.
+
+number = int(input("Enter Number Here: "))
+
+
+# Now try it with a while loop
diff --git a/1_beginner/chapter5/practice/even.py b/1_beginner/chapter5/practice/even.py
@@ -1,5 +1,5 @@
 # Even
 # Print every even number greater than 10
-# and less than 101
+# and less than 101 (10 ia included)
 
 # write code here
diff --git a/1_beginner/chapter5/practice/fibonnaci.py b/1_beginner/chapter5/practice/fibonnaci.py
@@ -0,0 +1,20 @@
+""" CHALLENGE PROBLEM!! NOT FOR THE FAINT OF HEART!
+
+The Fibonacci numbers, discovered by Leonardo di Fibonacci,
+is a sequence of numbers that often shows up in mathematics and,
+interestingly, nature. The sequence goes as such:
+
+1,1,2,3,5,8,13,21,34,55,...
+
+where the sequence starts with 1 and 1, and then each number is the sum of the
+previous 2. For example, 8 comes after 5 because 5+3 = 8, and 55 comes after 34
+because 34+21 = 55.
+
+The challenge is to use a for loop (not recursion, if you know what that is),
+to find the 100th Fibonnaci number.
+"""
+
+# write code here
+
+
+# Can you do it with a while loop?
diff --git a/1_beginner/chapter5/practice/prime.py b/1_beginner/chapter5/practice/prime.py
@@ -0,0 +1,28 @@
+"""
+
+Write a program to check if a number is prime or not. A prime
+number is one that is not divisible by any number other than
+1 and itself. For example, 11 is prime because it is not divisible
+by 2,3,4,5,...10 (i.e. 11/10, for example, is not an integer).
+
+Write a for loop to check if a number is prime or not.
+
+"""
+
+# write code here
+
+numer = int(input("Enter number here: "))
+
+"""
+Given a number less than or equal to 10 billion, see if you can check if it is
+prime in UNDER 2 SECONDS. The code you wrote above probably wont do that, so
+you will have to figure out a clever solution.
+
+NOTE: THE ABOVE IS A CHALLENGE PROBLEM, AND IS EXTRREEMMLY HARD TO DO.
+I COULDN'T DO IT OPTIMALY UNTIL I LEARNED HOW TO. If you can't
+figure out the solution, don't feel discouraged, its seriously a really
+hard problem (I have seen this asked to college students :O)
+
+"""
+
+# write code here
diff --git a/1_beginner/chapter5/practice/series.py b/1_beginner/chapter5/practice/series.py
@@ -0,0 +1,16 @@
+"""
+
+Here are some interesting results from mathematics that we can
+model with computer science.
+
+In class we added up 1 + 1/2 + 1/4 + 1/8 ...
+See if you can add up 1 + 1/3 + 1/9 + 1/27 + 1/81 ... in a similar fashion.
+What is the answer? What if, instead of 3, we use 5 (1 + 1/5 + 1/25 + 1/125...)
+7? Do you see a patter? (Note: make sure not to end up with an infinite loop).
+
+
+
+Also, try adding up 1 -1/3 + 1/5 - 1/7 + 1/9 - 1/11 ... 10 million times. then
+multiply this result by 4. What number is this close to?
+
+"""
diff --git a/1_beginner/chapter7/practice/replace.py b/1_beginner/chapter7/practice/replace.py
@@ -1,12 +1,14 @@
 """
 Replace
 
-Write a Python program to print a string
-from a given string where all occurrences
-of its first char have been changed to '$',
+Write a Python program that asks the user for a string
+and then prints a version of that string
+where all occurrences of its first char
+have been changed to '$',
 except the first char itself.
-Sample String : 'restart'
-Expected Result : 'resta$t'
+
+Sample Input: 'restart'
+Expected Output: 'resta$t'
 
 Adapted from W3Resource, problem 4:
 https://www.w3resource.com/python-exercises/string/
diff --git a/1_beginner/chapter7/practice/upper.py b/1_beginner/chapter7/practice/upper.py
@@ -1,6 +1,7 @@
 # Upper
 # Continuously ask a user to enter words.
-# (Make sure that the input given is actually just 1 word.)
+# You should remove leading/trailing whitespace, and then
+# make sure that the word is only made up of letters.
 # Store the words in a list.
 # Stop asking the user for words if they enter an empty string
 # (the string has no characters or is completely whitespace).
diff --git a/1_beginner/chapter7/solutions/replace.py b/1_beginner/chapter7/solutions/replace.py
@@ -1,13 +1,14 @@
 """
 Replace
 
-Write a Python program to print a string
-from a given string where all occurrences
-of its first char have been changed to '$',
+Write a Python program that asks the user for a string
+and then prints a version of that string
+where all occurrences of its first char
+have been changed to '$',
 except the first char itself.
 
-Sample String: 'restart'
-Expected Result: 'resta$t'
+Sample Input: 'restart'
+Expected Output: 'resta$t'
 
 Adapted from W3Resource, problem 4:
 https://www.w3resource.com/python-exercises/string/
diff --git a/1_beginner/chapter7/solutions/upper.py b/1_beginner/chapter7/solutions/upper.py
@@ -1,6 +1,7 @@
 # Upper
 # Continuously ask a user to enter words.
-# (Make sure that the input given is actually just 1 word.)
+# You should remove leading/trailing whitespace, and then
+# make sure that the word is only made up of letters.
 # Store the words in a list.
 # Stop asking the user for words if they enter an empty string
 # (the string has no characters or is completely whitespace).
diff --git a/2_intermediate/chapter10/practice/img_avg.py b/2_intermediate/chapter10/practice/img_avg.py
@@ -0,0 +1,46 @@
+""" Here is the challenge problem for 2d loops>
+Images are often represented as 3d arrays,
+where the rows and columns are the pixels in the image,
+and each pixel has an r, g, and b value.
+
+The interesting thing is that we can iterate over images.
+The challenge is, given an image, create a program that
+will return a different image where each pixel is the average
+of the pixels surrounding it in the original image.
+
+The neighbors of an image are all the pixels that surroun it,
+1 on each side, and 4 on the diagonals, for 8 in total. 
+Each pixel doesn't necessarily have 8 neighbors, though (think about why)
+
+The code to grab an image from the internet and make it
+into an array is given to you. The code also displays the new image
+you create in the end.
+
+NOTE: The image is 3 dimensional because each pixel has rgb values.
+To find the average value of all of a pixels neighbors, you must
+change the average of the red value to the red value, blue to blue, etc.
+For example, if the neighbors of a pixel with value [1,2,3]
+were [20,30,40] and [10,120,30], the new pixel that would replace the original one would be
+[15,75,35]
+"""
+
+from PIL import Image
+import requests
+import numpy
+import matplotlib.pyplot as plt
+
+url = "https://images.dog.ceo/breeds/waterdog-spanish/20180723_185544.jpg"
+img = numpy.array(Image.open(requests.get(url, stream=True).raw)).tolist()
+newimg = img
+transpose = numpy.transpose(img)
+
+plt.imshow(img)
+plt.show()
+
+# write code to create newimg here
+
+plt.imshow(newimg)
+plt.show()
+
+plt.imshow(transpose)
+plt.show()
diff --git a/2_intermediate/chapter10/solutions/img_avg.py b/2_intermediate/chapter10/solutions/img_avg.py
@@ -0,0 +1,88 @@
+""" Here is the challenge problem for 2d loops>
+Images are often represented as 3d arrays,
+where the rows and columns are the pixels in the image,
+and each pixel has an r, g, and b value.
+
+The interesting thing is that we can iterate over images.
+The challenge is, given an image, create a program that
+will return a different image where each pixel is the average
+of the pixels surrounding it in the original image.
+
+The neighbors of an image are all the pixels that surroun it,
+1 on each side, and 4 on the diagonals, for 8 in total. 
+Each pixel doesn't necessarily have 8 neighbors, though (think about why)
+
+The code to grab an image from the internet and make it
+into an array is given to you. The code also displays the new image
+you create in the end.
+
+NOTE: The image is 3 dimensional because each pixel has rgb values.
+To find the average value of all of a pixels neighbors, you must
+change the average of the red value to the red value, blue to blue, etc.
+For example, if the neighbors of a pixel with value [1,2,3]
+were [20,30,40] and [10,120,30], the new pixel that would replace the original one would be
+[15,75,35]
+"""
+
+from PIL import Image
+import requests
+import numpy
+import matplotlib.pyplot as plt
+
+url = "https://images.dog.ceo/breeds/waterdog-spanish/20180723_185544.jpg"
+img = numpy.array(Image.open(requests.get(url, stream=True).raw))
+newimg = img
+transpose = numpy.transpose(img)
+
+
+# write code to create newimg here
+def solution1():
+    """Iterating over the image here. i is a variable from 0 to the width of the image.
+	j is a variable that ranges from 0 to the height of the image. i is associated with
+	values"""
+    for i in range(len(img)):
+        for j in range(len(img[0])):
+            x_n = [0]
+            y_n = [0]
+
+            if i == 0:
+                x_n.append(1)
+            elif i == len(img) - 1:
+                x_n.append(-1)
+            else:
+                x_n.append(1)
+                x_n.append(-1)
+
+            if j == 0:
+                y_n.append(1)
+            elif j == len(img[0]) - 1:
+                y_n.append(-1)
+            else:
+                y_n.append(1)
+                y_n.append(-1)
+
+            r_avg = -1 * img[i][j][0]
+            g_avg = -1 * img[i][j][1]
+            b_avg = -1 * img[i][j][2]
+            c = -1
+
+            for x in x_n:
+                for y in y_n:
+                    r_avg += img[i + x][j + y][0]
+                    g_avg += img[i + x][j + y][1]
+                    b_avg += img[i + x][j + y][2]
+                    c += 1
+            r_avg = r_avg / c
+            g_avg = g_avg / c
+            b_avg = b_avg / c
+
+            newimg[i][j] = [r_avg, g_avg, b_avg]
+
+
+solution1()
+
+plt.imshow(newimg)
+plt.show()
+
+plt.imshow(transpose)
+plt.show()
diff --git a/2_intermediate/chapter11/practice/remove_duplicates.py b/2_intermediate/chapter11/practice/remove_duplicates.py
@@ -0,0 +1,15 @@
+# Write a function called remove_duplicates
+# The sole parameter of the function should be a list
+# The function should look through a list,
+# Find all duplicate elements, and remove them
+# Sort the resulting list
+# YOU MAY NOT USE THE set() function IN PYTHON.
+# Hint: To sort a list, use sorted(list)
+# Another hint: Use dict.removekeys(list)
+# To take the elements from a list,
+# and convert them to keys in a dictionary
+
+# Example: array = [1,1,2,5,4,6,12,3,4,6]
+# Result should print [1,2,3,4,5,6,12]
+
+# Write code here
diff --git a/2_intermediate/chapter11/solutions/remove_duplicates.py b/2_intermediate/chapter11/solutions/remove_duplicates.py
@@ -0,0 +1,32 @@
+# Write a function called remove_duplicates
+# The sole parameter of the function should be a list
+# The function should look through a list,
+# Find all duplicate elements, and remove them
+# Sort the resulting list
+# YOU MAY NOT USE THE set() function IN PYTHON.
+# Hint: To sort a list, use sorted(list)
+# Another hint: Use dict.fromkeys(list)
+# To take the elements from a list,
+# and convert them to keys in a dictionary
+
+# Example: array = [1,1,2,5,4,6,12,3,4,6]
+# Result should print [1,2,3,4,5,6,12]
+
+# Write code here
+
+list1 = [1, 1, 2, 5, 4, 6, 12, 3, 4, 6]  # Define your list
+
+
+# Define your Function
+def remove_duplicates(array):
+    my_list = list(dict.fromkeys(array))
+    # Converts the list into a dictionary.
+    # Fromkeys(array) turns each item into a key
+    # There cannot be multiple keys,
+    # So all the duplicate keys are removed
+    # Convert the keys back into a list
+    return sorted(my_list)
+    # Returns the sorted list of keys that are not duplicate.
+
+
+print(remove_duplicates(list1))  # Call the function
