Strings

• cats = "RickyandLucy"

Strings

• cats is a string literal
• sequence
  • cats[0], cats[1],
  • 0 and 1 are indexes
  • len()

pets = ""
cats = "RickyandLucy"
pets = cats
print(pets, end= " ")
print(len(pets))
print("Intials: \n\t", pets[0], "and", pets[8])

More on Strings

• \
• + concatenate

kitty_one = "Ricky"
kitty_two = "Lucy"
cats = kitty_one + 'and' + kitty_two
cats_2 = "Ricky" \ 
         "and" \ 
         "Lucy"
print(cats)
print(cats_2)

formatting strings

• f-strings: builds a string
• expression inside the curly brace
  • can have multiple expressions
• ' ' are important
• =

my_string = (f' 2 + 3 equals {2+3}')
print(my_string)
print(f' multiplication {12 * 123 = :f}')

• format specifications in textbook

Airthmetic Expressions

• expression: evaluates to a value
• literal
  • string, literal, float
• operators
  • +, -, *, /, **
  • unary
• precedence rules

result = -2 * 6 + 2**3 * 7

Type conversions

• implicit
  • at least one float operand in expression result in a float
• explicit
  • int() note: no rounding
  • float()
  • str()

Some examples

quantity = 10
value = 15.5
worth = quantity * value 
# what type is worth?
print(worth)

number1 = int(input("Enter a number "))
number2 = int(input("Enter another number "))
print(number1 + number2)
print(float(number1) + number2)
print(number1)

Compound Operators

• often want to increment or decrement a variable

count = count + 1
chances = chances -1

• compound operators are shorthand

count +=1
chances -= 1

Divison

• /
  • returns a float, even when two integer operands
• //
  • divides but gives only the whole number result
  • returns integer if both operands are integers
  • returns float is one or both operands are floats

print(9/2)
print(9//2)
print(9//2.0)

Modulo

• %
  • returns the remainder
  • 2 integer operands, returns integer
  • one or both float operands, returns float.

print(34 % 7)
print (34 // 7)

Math Module

• module: Python code located in another file
• import a module so can use it
  • top of the file
• functions from math module
  • call and arguments
  • math.sqrt(5)
  • see textbook for more functions

import math

number = 5.6
print(math.ceil(number))