Calling Built-In Functions (CSCI-UA.0002-008

Built-In Functions

Based on the previous slides, name some functions that we've learned so far →

(Remember, a function is a named sequence of statements that performs a specific task or useful operation)

print
type
int
float
str

Using Built-In Functions

How do you use (call) built-in functions in your code? How would you call the function, str, on a value, 300 (that is, convert 300 to a string)? →

"""
1. start with the function name, str
2. use parentheses to signify that you're calling a function
3. within those parentheses, put in the value that you're passing in, 300
"""
str(300)

Using Built-In Functions with Multiple Input Values

again start with the function name
use parentheses to signify that you're calling a function
within those parentheses, put in the values, separated by commas, that you're passing in

"""
print can take multiple values as inputs
this contrived example shows two strings as inputs to print
"""

print("Hi ", "there")

Some Terminology

call - using a function in your code, executing a function
arguments - the actual literal values that a function is called with; 25 is the argument in print(25)
parameters - within the function itself, the names given to the values passed in (we'll see more about this when we create our own functions)
passing arguments into a function - providing input values to a function
return value - the value that's given back to your program after calling a function (returning a value doesn't mean printing out a value)

Talkin' the Talk

Using this code as an example:

num = "5"
x = int(num)

what is the name of the function being called? →
what are the arguments passed in to the function? →
what value is returned from this function call? →

int
num, or the string, "5"
the integer, 5

Talkin' the Talk 2

length = 10
width = 7
print(length, width)

what is the name of the function being called? →
what are the arguments passed in to the function? →

print
the integers, length and width (10 and 7 respectively)

Note that print does not return a value to your program; rather it prints values to the screen.

Composing Functions

you can call functions within functions
the value returned by the inner function calls are what's used as arguments to the outer function call

t = type(str(5 + 5))
print(t)

What is printed out by this program? →

The type of the result of calling str(5 + 5), which turns out to be? →

<class 'str'>

Calling Built-In Functions