JamCoders Day 3 Lecture 1¶

Boaz Barak¶

Going deeper into functions

Ignore this section¶

def md_table(array):
    """ the same input as above """

    nl = "\n"
    t = 30

    markdown = nl
    markdown += f"| {' | '.join([x.ljust(t-2) for x in array[0]])} |"

    markdown += nl
    markdown += f"| {' | '.join(['-'*(t-2)]*len(array[0]))} |"

    markdown += nl
    for entry in array[1:]:
        L = [entry[0].ljust(t-2)] + [ f'<font color="blue"><b>{x}</b></font>'.ljust(t-2) for x in entry[1:]]
        markdown += f"| {' | '.join(L)} |{nl}"

    return markdown

from IPython.display import Markdown, display
from IPython.display import clear_output

display(Markdown(md_table([["Name","Age"],["Boaz","48"]])))

MARKDOWN = ""
DEBUG = True
def state(code,line,variables,depth):
    if not DEBUG: return
    lines = code.split('\n')
    lines[line] += " #<-------"     
    code = "\n".join(lines)
    global MARKDOWN
    global DEPTHS
    md_lines = MARKDOWN.split("\n")
    if depth>0:
        found = [i for i,x in enumerate(md_lines) if x[:9]=="```python" ]
        if len(found)>depth:
            md_lines = md_lines[:found[depth]]
        md = "\n".join(md_lines)+"\n"
    else:
        md = ""
    md += rf"""```python
    {code}```
    
    """
    table = [["Variable", "Value"]] + [[k,v] for k,v in variables.items()]
    md += md_table(table) +"\n\n\n"
    MARKDOWN = md
    clear_output()
    #if depth: print(found, len(md_lines))
    display(Markdown(MARKDOWN))
    if input("---"*depth+":")=="q":
        raise Exception()

def lookinto(name):
    global DEBUG
    DEBUG=True
    globals()[name] = globals()[name+"_"]
    
def normal():
    global DEBUG
    DEBUG = False

code_m ="""
def multiply(a,b):
    result = 0
    for i in range(b):
        result += a
    return result
"""

import inspect

def up_locals():
    frame = inspect.currentframe()
    return frame.f_back.f_back.f_locals
        
        
def multiply_(a,b,depth=0):
    def s(i): 
        state(code_m,i+1,{k:v for k,v in up_locals().items() if k!="s" and k!="depth"},depth)
    result = 0 #1
    s(1)
    for i in range(b): #2
        s(2)
        result += a #3
        s(3)
    s(4)
    return result #4

code_e = """
def exponent(x,y):
    result = 1
    for i in range(y):
        result = multiply(result,x)
    return result
"""

def exponent_(x,y,depth=0):
    def s(i): 
        state(code_e,i+1,{k:v for k,v in up_locals().items() if k!="s" and k!="depth"},depth)
    result = 1 #1
    s(1)
    for i in range(y): #2
        s(2)
        s(3)
        result = multiply(result,x, depth=1) #3
    s(4)
    return result #4

Calling functions example¶

Question: Write function multiply that takes inputs integers $a,b$ and returns $a\times b$ without using *

def multiply(a,b):
    ...

# question: multiply two integer without using *
def multiply(a,b):
    result = 0
    for i in range(b):
        result += a
    return result

multiply(3,5)

15

Diving in¶

lookinto("multiply")

multiply(3,5)

def multiply(a,b):
    result = 0
    for i in range(b):
        result += a
    return result #<-------

:

15

normal()

Question: Write a function exponent that takes as input two integers $x,y$ and returns $x^y$ without using * or **. It can use multiply

def exponent(x,y):
    ...

def exponent(x,y):
    result = 1
    for i in range(y):
        result = multiply(result,x)
    return result

exponent(2,3)

8

lookinto("exponent")

exponent(2,3)

def exponent(x,y):
    result = 1
    for i in range(y):
        result = multiply(result,x)
    return result #<-------

:

8

More function examples¶

def passing_grade(score):
    if score > 50:
        return True
    return False
print(passing_grade(60))
print(passing_grade(25))

True
False

Reminder - difference between print and return¶

def passing_grade(score): # print version
    if score > 50:
        print("True")
    print("False")

if passing_grade(99):
    print("That's a great grade")

True
False

def passing_grade(score): # print version
    if score > 50:
        return True
    return False

if passing_grade(99):
    print("That's a great grade")

That's a great grade

Using a function¶

Suppose we have the passing_grade function above. Write a function passed that takes as input two lists students and grades and prints the names of the students that passed.

def passed(students,grades):
    ...

def passed(students,grades):
    n = len(students)
    for i in range(n):
        if passing_grade(grades[i]):
            print(students[i])

students = [ "Bereket", "Annamira", "Elijah", "Orr", "Jabari", "Annakai", "Tyler" ]

# let's make grades random for fairness
import random
grades = []
for i in range(len(students)):
    grades.append(random.randint(1,100))

grades

[50, 98, 27, 32, 6, 18, 49]

passed(students,grades)

Annamira

Functions (variable scoping)¶

# Variables inside a function have no relation to variables outside the function
# See what happens when "i" is printed inside and outside the function

i = 0
def func(x):
    i = 10
    print("i=",i, "x=",x)
    
func(5)
print("i=",i)

i= 10 x= 5
i= 0

# Variables across functions have no relation to each other
# A variable declared inside a function will have no relation to outside the function
# Why is there an error?

def func1(x):
    j = 10
    print("j=",j, "x=",x)

def func2(x):
    j = 5
    func1(x)
    print("x=",x)
    
func2(3)
print(j)

j= 10 x= 3
x= 3

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Input In [27], in <cell line: 15>()
     12     print("x=",x)
     14 func2(3)
---> 15 print(j)

NameError: name 'j' is not defined

# Why is this the output?

k = 0
for i in range(3):
    print(k)

0
0
0

# How about here?

k = 0
for i in range(3):
    k = 6
    print(k)

6
6
6

Variable	Value
a	3
b	5
result	15
i	4

Variable	Value
x	2
y	3
result	8
i	2

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