Chapter 2 - Input, Processing, & Input

print ()

displays text

Why must the text in the print() function be enclosed in quotes?

so the interpreter identifies it as a string

string

sequence of characters; can include letters, numbers and symbols

True or false: arithmetic expressions can be performed within a print() command

true

True or false: arithmetic expressions inside the print() function must be enclosed in quotes

false

comments

short notes placed in different parts of the program, explaining how those parts of the program work; started by the # symbol and ignored by the interpreter

guidelines for comments

• should be clear and concise

• don’t comment on things that are self-explanatory

• update comments as the code evolves

• use comments to explain logic

variable

a container for storing data values (e.g. strings or numbers)

• created and assigned using “=”

• can consist of alphabets, digits, and underscores

• cannot have special symbols and cannot begin with a number

camelCase

the variable name begins with lowercase letters, and the first character of the second and subsequent words is written in uppercase

snake_case

underscores replace spaces in separating words in variable names

How can you display multiple items with one print statement?

by separating the items with commas

data types

categories of values in memory

int

value written as a whole number without a decimal point

float

value written with a decimal point

str

sequence of characters

input()

used to read a line of input from the user; usually displays a prompt message to guide the user on what information to provide

What data type does the input() function always return?

string

What built-in functions can be used to convert between data types?

• int(item) - converts to integer

• float(item) - converts to float

What does the item have to be for type conversion to work?

a valid numeric value

%

remainder

**

exponent

True or false: the Python interpreter followers order of operations

true

How can you break a statement into multiple lines?

using backslash (\)

hard-coding

storing values in variables that are not dependent on user input

• makes the code hard to change

• good for learning but not for applications

multiple assignment

assigning values to multiple variables in a single statement

What does combining different data types in a print statement require?

converting one type to another

f-string (formatted string literal)

allows you to embed expressions directly inside strings

• gives a more flexible and readable output format that using the str() function

f-string format

print("‘{<index>:<padding character><alignment character><block size><precision>}’)

What does it mean for a string to be immutable?

it cannot be changed after creation

string concatenation

combining strings using the + operation

• ex: greeting = “Hello” + “ “ + “World”

escape sequence

a sequence of characters that when used inside a character or string, is converted into another character or series of characters that may be difficult or impossible to express directly

\’

single quote

\\’

double quote

\\

backslash

\n

newline

\r

carriage return

\t

horizontal tab

\b

backspace

\v

vertical tab

\0

null character

index

position of a character inside a string

What does indexing start at for the first character?

0

What symbol do you use to access a character at a specific index?

square brackets [ ]

negative indexing

accessing characters from the back end of the string

string slicing

allows you to obtain a substring by specifying a range of indices

string slicing format

string [start:stop]

• start is inclusive

• stop is exclusive

str.lower()

converts all characters to lowercase

str.upper()

converts characters to uppercase

str.strip()

removes leading and trailing whitespace

str.split()

splits the string into a list of substrings

str.join(iterable)

joins elements of an iterable to a single string

str.replace(old, new)

replaces occurrences of a substring

str.find(sub)

returns the lowest index of the substring

str.startswith(prefix)

checks if the string starts with a prefix

str.endswith(suffix)

checks if the string ends with a suffix

len(obj)

returns the length of an object