Week 0: Functions, Variables

Hello Bison in Python

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print("Hello Bison!")

Functions

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• We just used the print function.

• Argument: value passed to a function.

• Side effects: printing to the console.

Bugs and Debugging

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• Bugs: mistakes in the code.

• Debugging: finding and fixing bugs.

Return values and Variables

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• Return values: values returned by functions.

• Variables: store values for later use.

Comments and Pseudocode

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• Comments: notes to self and others.

• Pseudocode: planning code before writing it.

Multiple function arguments

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• String: a sequence of characters.

• Concateation: combining strings.

Table of Data Types

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Named Parameters

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Documentation for print function

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print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

• *objects: zero or more objects to print.
• sep: how to separate objects.
• end: what to print at the end.
• file: where to print.
• flush: whether to forcibly flush the stream.

Parameters vs Arguments

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• Parameters: variables in the function definition.
• Arguments: values passed to the function.

Small pieace of code to demonstrate how to change the end parameter behavior

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print("Hello ", end="")
print("Bison!")

The expected output is Hello Bison!.

Named parameters vs Positional parameters

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• Named parameters: they are optional and can be passed in any order.
• Positional parameters: they are required and must be passed in the correct order.

Escaping Characters

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• Escape character: backslash ().

f-strings

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• f-string: formatted string literal.

Example of code using f-strings

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name = "Bison"
print(f"Hello, {name}!")

The expected output is Hello, Bison!.

String Methods

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• .strip(): remove whitespace.

• .capitalize(): capitalize the first letter.

• .title(): capitalize the first letter of each word.

• .lstrip(): remove whitespace from the left.

• .rstrip(): remove whitespace from the right.

Example of code using .strip() and .title()

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name = input("What's your name? ").strip().title()

print(f"Hello, {name}!")

Style

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• Style: how code looks and is organized.

• PEP 8: Python Enhancement Proposal 8.

split

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• .split(): split a string into a list.

Example of code using .split()

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names = input("Enter names separated by commas: ").split(", ")
print(names)

Expected output: ['Alice', 'Bob', 'Charlie'].

Integers and Operators

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• Integer: whole numbers.

• Operators: symbols that perform operations.

Table of Operators

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Interactive mode

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The interactive mode is a way to run Python code line by line.

Calculator.py

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x = input("What's x? ")
y = input("What's y? ")

z = x + y
print(z)

Type Conversion

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• Type conversion: converting one data type to another.

• int(): convert to integer.

Example of code using int()

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x = int(input("What's x? "))
y = int(input("What's y? "))

print(x + y)

Foating Point Values

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• Floating point values: decimal numbers.

• float(): convert to floating point.

Example of code using float()

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x = float(input("What's x? "))
y = float(input("What's y? "))

print(x + y)

Rounding Numbers

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• round(): round a number to a specified number of decimal places.

round(number[, ndigits])

Example of code using round()

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x = float(input("What's x? "))
y = float(input("What's y? "))

z = round(x + y)

print(z)

Numeric Formatting

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• f-string: formatted string literal.

Example of code using f-string to format a number

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x = float(input("What's x? "))
y = float(input("What's y? "))

z = round(x + y)

print(f"{z:,}")

Division

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• /: division.

Example of code using / and //

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x = float(input("What's x? "))
y = float(input("What's y? "))

z = x / y

print(f"{z:.2f}")

Defining Functions

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• def: define a function.

Example of code defining a function

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def main():
    name = input("What's your name? ")
    hello(name)


def hello(to="Bison"):
    print("Hello ", to)


main()

Scope

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• Scope: where a variable is accessible.

Return Values

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• return: return a value from a function.

Example of code using return

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def main():
    x = int(input("What's x? "))
    print("x squared is", square(x))

def square(n):
    return pow(n, 2)

main()