All language subtitles for 004用户输入

all right everybody

in this topic

I'm going to show you how we can accept user input

in Python we use the input function

it's a function that prompts the user to enter in data

and it returns the enter data as a string

here's an example

to accept user input we will call the input function

when I run this program

we need to enter in data to our console window

like so then hit enter

however we need a prompt

we need to tell the user what we want them to type in

so let's ask a question

our prompt will be within

let's say what is your name

let's try this again

what is your name

I can type in something

why don't you go ahead and type in your full name

then hit enter

now with this input

we're not quite doing anything with it

the input function is going to return some data

as a string

we can assign it to a variable if we would like

let's create a variable of name

name equals our user input

then once we have our name

let's print a message

I'll use an F string

we will print hello

add a placeholder

then insert our name variable within that placeholder

let's try this

what is your name

type in your name

hit enter hello

whatever your name is

let's try a different name

I will pick SpongeBob

many people are familiar with SpongeBob

hello SpongeBob

this time we will ask a user how old they are

let's assign a variable of age equals

accept some user input

we need a prompt within quotes

how old are you

once we have our age variable

let's print I'll use an F string

U r at a placeholder

our variable age

years old

what is your name

type in your name

how old are you

let's say that I'm 25

hello

whatever your name is you are whatever your age is

years old

all right so let's say that it's our birthday

before we print our age variable let's say

happy birthday

since I'm not inserting any variables

within this print statement

this doesn't need to be an F string

you want to use an F string

if you want to insert variables

before we display the user's age

let's take the user's age and increase it by 1

we could say age equals age plus 1

but there's one problem with this

type in a name

how old are you

type in an age

and we have a problem

we have a type error

can only concatenate strings not integers to strings

when we accept user input

we store that input as a string

before we increment our age by 1

we'll need to convert it to an integer

we can't normally use strings

within arithmetic expressions

but we can do that with integers and floats though

after we accept some user input for our age variable

we could take our age variable

and typecast it as an integer

which we talked about in the previous lesson

so let's say age equals our age

after we typecast it

then incremented by one

so type in your name

type in an age

and we get this message

hello your name

happy birthday you are whatever your age is years old

so strings we can't normally use

with arithmetic expressions

we would have to typecast it to an integer or afloat

however we could condense some of these steps

we're taking up an extra line

to typecast our age as an integer

what we could do instead

is that when we accept our user input

we can enclose the input function

within a typecast to INT

and that would work the same

type in your name

type in an age

and this works the same

and it takes less lines of code

and is more readable I would say

when we accept user input

it returns that input as a string data type

then we just have to

typecast it to another data type if we need to

and in this case for age we do

now we'll go over a couple exercises

because it's important to practice what you've Learned

in this first exercise

we're going to calculate the area of a rectangle

we need to prompt the user to enter in a

length and the width of a rectangle

so we will create a variable of length

we will accept some user input using the input function

what is our prompt

let's say enter the length

let's do this with width

I'll just copy and paste what we have

width equals enter the width

so we have the length and the width

to get the area of a rectangle

we have to multiply the length by the width

so let's say area

equals our length variable

now to use multiplication you use an asterisk

we'll discuss different arithmetic

operators in the next lesson

so we have length times width

that is the area

I'm going to print our area

because I need to test something

enter the length let's say 5

5 inches 5 centimeters doesn't matter

enter the width 6

we get a type air

can't multiply sequence by non INT

non integer of type string

when we accept user input it

returns a value of the string data type

we can't use those strings in arithmetic expressions

we're multiplying the length times the width

we would need to typecast them as an integer or afloat

since we're working with basic geometry

such as calculating the area

let's do float

so let's type cast our user input as a float

for both length and width

okay let's try this again

let's say 5 times six

the area that's returned to us is 30

30 point 0 this result contains a decimal

it's a floating point number a float

so when we print the area

I'll use an F string this time

the area is

I'll add a placeholder

display our area variable

let's add a unit of measurement afterwards

I'll pick centimeters

now since we're working with areas

if we would like to technically be accurate

so we could say to the power of two

or we could add a superscript

so if you would like superscript 2

and you're on Windows

make sure numlock is on hold alt

then type on the numpad 0178

so we have a superscript of 2

again it's not really necessary for this lesson

I just think it'd be cool to include it

because then it's technically accurate

all right let's say that the length is 6.1

and the width is 7.2

the area is 43.92 cm squared

because we're working with areas

let's cover a second exercise

this time we will create a shopping cart program

exercise 2

we're going to create a shopping cart program

we need three variables an item a price and a quantity

of those items

we will create a variable of item

we will accept some user input

what item would you like to buy

what are we trying to purchase

we'll keep the data type of the user input as a string

then we need a price

what is the price of each item we're buying

use the input function

what is the price

a price should be a floating point number

for example we might have dollars and cents

we need a decimal

so let's type cast our input as a float

then a quantity

we will accept some user input

our prompt will be

how many

would you like

quantities they should be whole numbers

let's typecast our input as an integer

then we will have a total

what's the total that we have to pay

so let's take the price of each item

use an asterisk for multiply r quantity

then let's do a test run

let's print our total

what item would you like to buy let's say a pizza

what is the price

1099

how many would you like

I would like five pizzas

and our total is 54.95

let's say that before we display the total

let's print the following

I'll use an F string

you have bought

insert a placeholder

display our quantity

x

item or items I'll add s

then we will print I'll use an F string again

your total is

display our total

what item would you like to buy

I would like to buy a pizza

what is the price

1099 how many would you like

I would like nine pizzas

they're all for me I'm gonna eat all of them

you have bought 9x pizzas your total is 98.91

let's add a unit of currency before this

pick unit of currency before displaying the total

I'll pick American dollars

I would like to buy pizza

what is the price

nine dollars ninety nine cents

how many would you like I would like a dozen pizzas 12

you have bought 12 x pizzas

your total is 119 dollars and 88 cents

alright everybody

that is how to accept user input in Python

and we've covered a few exercises

in the next topic

we're going to create a Mad Libs game

and that is how to accept user input in Python