Create 20240220-lecture-code.py

Term-04/intro-cs/20240220-lecture-code.py

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+# COPY OF CODE FROM LECTURE 4:
+
+#########################
+## EXAMPLE: combinations of print and return
+## Python Tutor link: http://www.pythontutor.com/visualize.html#code=def%20is_even_with_return(%20i%20%29%3A%0A%20%20%20%20%22%22%22%20%0A%20%20%20%20Input%3A%20i,%20a%20positive%20int%0A%20%20%20%20Returns%20True%20if%20i%20is%20even,%20otherwise%20False%0A%20%20%20%20%22%22%22%0A%20%20%20%20print('with%20return'%29%0A%20%20%20%20remainder%20%3D%20i%20%25%202%0A%20%20%20%20return%20remainder%20%3D%3D%200%0A%0Ais_even_with_return(3%29%20%0Aprint(is_even_with_return(3%29%20%29%0A%0Adef%20is_even_without_return(%20i%20%29%3A%0A%20%20%20%20%22%22%22%20%0A%20%20%20%20Input%3A%20i,%20a%20positive%20int%0A%20%20%20%20Does%20not%20return%20anything%0A%20%20%20%20%22%22%22%0A%20%20%20%20print('without%20return'%29%0A%0Ais_even_without_return(3%29%0Aprint(is_even_without_return(3%29%20%29%0A&cumulative=false&curInstr=0&heapPrimitives=false&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false
+#########################
+def is_even_with_return( i ):
+    """ 
+    Input: i, a positive int
+    Returns True if i is even, otherwise False
+    """
+    print('with return')
+    remainder = i % 2
+    return remainder == 0
+
+is_even_with_return(3) 
+print(is_even_with_return(3) )
+
+def is_even_without_return( i ):
+    """ 
+    Input: i, a positive int
+    Does not return anything
+    """
+    print('without return')
+    remainder = i % 2
+
+is_even_without_return(3)
+print(is_even_without_return(3) )
+
+# Simple is_even function definition
+def is_even( i ):
+    """ 
+    Input: i, a positive int
+    Returns True if i is even, otherwise False
+    """
+    remainder = i % 2
+    return remainder == 0
+
+# Use the is_even function later on in the code
+print("All numbers between 0 and 20: even or not")
+for i in range(20):
+    if is_even(i):
+        print(i, "even")
+    else:
+        print(i, "odd")
+
+#########################
+## EXAMPLE: applying functions to repeat same task many times
+#########################
+def bisection_cuberoot_approx(x, epsilon):
+    """
+    Input: x, an integer
+    Uses bisection to approximate the cube root of x to within epsilon
+    Returns: a float approximating the cube root of x
+    """
+    low = 0.0
+    high = x
+    guess = (high + low)/2.0
+    while abs(guess**3 - x) >= epsilon:
+        if guess**3 < x:
+            low = guess
+        else:
+            high = guess
+        guess = (high + low)/2.0
+    return guess
+
+x = 1
+while x <= 10000:
+    approx = bisection_cuberoot_approx(x, 0.01)
+    print(approx, "is close to cube root of", x)
+    x *= 10
+
+
+#########################
+## EXAMPLE: functions as arguments
+## Python Tutor link: http://www.pythontutor.com/visualize.html#code=def%20func_a(%29%3A%0A%20%20%20%20print('inside%20func_a'%29%0A%0Adef%20func_b(y%29%3A%0A%20%20%20%20print('inside%20func_b'%29%0A%20%20%20%20return%20y%0A%0Adef%20func_c(z%29%3A%0A%20%20%20%20print('inside%20func_c'%29%0A%20%20%20%20return%20z(%29%0A%0Aprint(func_a(%29%29%0Aprint(5%2Bfunc_b(2%29%29%0Aprint(func_c(func_a%29%29%0A&cumulative=false&curInstr=0&heapPrimitives=false&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false
+#########################
+def func_a():
+    print('inside func_a')
+
+def func_b(y):
+    print('inside func_b')
+    return y
+
+def func_c(z):
+    print('inside func_c')
+    return z()
+
+print(func_a())
+print(5+func_b(2))
+print(func_c(func_a))
+
+
+#########################
+## EXAMPLE: returning function objects
+## Python Tutor link: http://www.pythontutor.com/visualize.html#code=def%20f(%29%3A%0A%20%20%20%20def%20x(a,%20b%29%3A%0A%20%20%20%20%20%20%20%20return%20a%2Bb%0A%20%20%20%20return%20x%0A%20%20%20%20%0Aval%20%3D%20f(%29(3,4%29%0Aprint(val%29%0A&cumulative=false&curInstr=0&heapPrimitives=false&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false
+#########################
+def f():
+    def x(a, b):
+        return a+b
+    return x
+
+# the first part, f(), returns a function object
+# then apply that function with parameters 3 and 4
+val = f()(3,4)
+print(val)
+
+
+
+#########################
+## EXAMPLE: shows accessing variables outside scope
+#########################
+def f(y):
+    x = 1
+    x += 1
+    print(x)
+x = 5
+f(x)
+print(x)
+
+def g(y):
+    print(x)
+    print(x+1)
+x = 5
+g(x)
+print(x)
+
+def h(y):
+    pass
+    #x += 1 #leads to an error without line `global x` inside h
+x = 5
+h(x)
+print(x)
+
+
+#########################
+## EXAMPLE: hader scope example from slides
+## Python Tutor link: http://www.pythontutor.com/visualize.html#code=def%20g(x%29%3A%0A%20%20%20%20def%20h(%29%3A%0A%20%20%20%20%20%20%20%20x%20%3D%20'abc'%0A%20%20%20%20x%20%3D%20x%20%2B%201%0A%20%20%20%20print('in%20g(x%29%3A%20x%20%3D',%20x%29%0A%20%20%20%20h(%29%0A%20%20%20%20return%20x%0A%0Ax%20%3D%203%0Az%20%3D%20g(x%29&cumulative=false&curInstr=0&heapPrimitives=false&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false
+#########################
+def g(x):
+    def h():
+        x = 'abc'
+    x = x + 1
+    print('in g(x): x =', x)
+    h()
+    return x
+
+x = 3
+z = g(x)
+
+
+#########################
+## EXAMPLE: complicated scope, test yourself!
+## Python Tutor link: http://www.pythontutor.com/visualize.html#code=def%20f(x%29%3A%0A%20%20%20x%20%3D%20x%20%2B%201%0A%20%20%20print('in%20f(x%29%3A%20x%20%3D',%20x%29%0A%20%20%20return%20x%0A%0Ax%20%3D%203%0Az%20%3D%20f(x%29%0Aprint('in%20main%20program%20scope%3A%20z%20%3D',%20z%29%0Aprint('in%20main%20program%20scope%3A%20x%20%3D',%20x%29%0A%0Adef%20g(x%29%3A%0A%20%20%20%20def%20h(x%29%3A%0A%20%20%20%20%20%20%20%20x%20%3D%20x%2B1%0A%20%20%20%20%20%20%20%20print(%22in%20h(x%29%3A%20x%20%3D%20%22,%20x%29%0A%20%20%20%20x%20%3D%20x%20%2B%201%0A%20%20%20%20print('in%20g(x%29%3A%20x%20%3D%20',%20x%29%0A%20%20%20%20h(x%29%0A%20%20%20%20return%20x%0A%0Ax%20%3D%203%0Az%20%3D%20g(x%29%0Aprint('in%20main%20program%20scope%3A%20x%20%3D%20',%20x%29%0Aprint('in%20main%20program%20scope%3A%20z%20%3D%20',%20z%29%0A&cumulative=false&curInstr=0&heapPrimitives=false&mode=display&origin=opt-frontend.js&py=3&rawInputLstJSON=%5B%5D&textReferences=false
+#########################
+def f(x):
+   x = x + 1
+   print('in f(x): x =', x)
+   return x
+
+x = 3
+z = f(x)
+print('in main program scope: z =', z)
+print('in main program scope: x =', x)
+
+def g(x):
+    def h(x):
+        x = x+1
+        print("in h(x): x = ", x)
+    x = x + 1
+    print('in g(x): x = ', x)
+    h(x)
+    return x
+
+x = 3
+z = g(x)
+print('in main program scope: x = ', x)
+print('in main program scope: z = ', z)