I have created two functions namely inputData(): and validateNumber():
In the inputData() function I enter a value and stores it in a variable called number. And then I want to pass that parameter to validateNumber(): function. But it isn't work :(
It would be fine if anyone explain me the error :)
Regards.
Here's the code:
def inputData():
number = int(input("Enter a Number: "))
print(number)
return number
def validateNumber(number):
n=2
while number > n:
if number%n==0 and n!=number:
print("Not Prime")
break
else:
print("Prime")
break
return number
inputData()
validateNumber()
You need to perform the function call as follows:
validateNumber(inputData())
or
number = inputData()
validateNumber(number)
with def validateNumber(number) you are telling python that the function validateNumber must receive one parameter when it is called. But, you are not passing the parameter to it when you call it.
If you are new to programming, check this tutorial: Python Functions, to understand:
What are functions
How to define them
How to use them.
You need to store the value of inputData() function in some variable then pass it to second function like this
>> number = inputData()
>> validateNumber(number)
You're not passing the inputted number to the validate function.
returned_input_number = inputData()
validateNumber(returned_input_number)
Also, I find it a bit odd that your validateNumber function returns a number. It might be better to return True or False (depending on if the number is valid or not). Either that, or maybe 'validate' is the wrong name for the function.
Related
quick question since I was not able to find a sufficient answer online.
Following code snippet:
def Credentials (x, y):
list = [("test", 1234), ("test2", 4567)]
for list in list:
if list[0] == userinput1 and list[1] == userinput2:
print("success")
return True
else:
print("error")
return False
userinput1 = str(input("provide username: "))
userinput2 = int(input("provide PW: "))
Credentials(userinput1, userinput2)
I do not fully understand why the boolean values True and False will return the print statements. I know that we use return statements to work with functions in our main program and that we could also define variables and return those. But why exactly does returning the booleans will give us the print outputs?
Many thanks in advance.
Short answer: It does not
In your function/in my function shown below,
def returnBools():
(print) print('Printed')
(return) return True
print(returnBools())
The print function and the return statement are actually two different things. The print has nothing to do with the return, and the return statement does not in anyway trigger the print function.
Additionally, the way we call the function can effect the output
For example, printing the function print(returnBools()) will display the returned value along with any print functions in our function
output
Printed
True
But say we did not print the function and only called it. returnBools(). The returned value will not be showed in this case and only the printed values will.
output
Printed
I cannot figure out how do I pass the result of one method to another one. The first method generates new array, filled with numbers in whatsoever size. The second method is supposed to sort all the numbers within the array, which have been previously generated in method no.1. I am getting an error "NameError: name 'value' is not defined". Is this because the list returns None? If so, how do I make it work? I would appreciate any help.
def Display_Details1(self):
value = []
num1 = int(input("Select array size: "))
seed(0)
for i in range(num1):
value.append(random.randint(1, 99))
print(value)
return value
print(self.generate)
def Display_Details2(self):
value.sort()
return value
print(self.sort)
Passing a variable from one function as argument to another function can be done like this:
First off, define functions like this:
def function1():
global a
a=input("Enter any number\t")
def function2(argument):
print ("this is the entered number - ",argument)
call the functions like this
Then call them like this:
function1()
function2(a)
I'm having a hard time to understand how to work with functions - I can make then but after that I don't know how to use them. My question is how can I print this code with a function?
string = "Hello"
reverse = string[::-1]
print(reverse)
I tried putting it in a function but I cannot make it print Hello.
def reverse_a_string(string):
string = "Hello"
reverse = string[::-1]
print(reverse)
also tried this
def reverse_a_string(string):
string = "Hello"
reverse = string[::-1]
print(reverse)
Nothing seems to work. I'm having same problem with this as well.
total = 0
def length(words):
for i in words:
total += 1
return total
Functions without a return value
Functions that just take action or do something without returning a value (for example, print).
Functions that don't return a value can be defined like that:
def sayHello():
print "Hello!"
And can be used (called) like that:
sayHello()
And the output will be:
Hello!
Function parameters
A function can also receive parameters (type of variables) from the caller. It's better to demonstrate it with an example.
A function that receives a name and greets this name:
def sayHelloTo(name):
print "Hello", name
It can be called like that:
sayHelloTo("Yotam")
And the output will be:
Hello Yotam
The parameters are the function's input.
Functions with a return value
Other functions, unlike sayHello() or sayHelloTo(name) (that just do something) can return a value. For example, let's make a function that rolls a dice (returns a random number between 1 and 6).
from random import randint
def rollDice():
result = randint(1, 6)
return result
The return keyword just sets the output value of the function and exits the function. An example use of the rollDice function will be:
dice = rollDice()
print "The dice says", dice
When the function hits a return keyword, it finishes and the return value (in our case, the variable result) will be placed instead of the function call. Let's assume randint(1, 6) has produced the number 3.
Result becomes 3.
Result is returned.
Now, instead of the line:
dice = rollDice()
We can treat the line as:
dice = 3
(rollDice() was replaced with 3)
Functions with parameters and a return value
Some functions (for example, math functions) can take inputs AND produce outputs. For example, let's make a function that receives 2 numbers and outputs the greater one.
def max(a,b):
if a > b:
return a
else:
return b
What it does is pretty clear, isn't it? If a is greater, it returns the value of it. Otherwise, returns the value of b.
It can be used like that:
print max(4, 6)
And the output will be:
6
Now, your case
What you want to do is a function that reverses a string. It should take 1 parameter (input) - the string you want to reverse, and output 1 value - the reversed string. This can be accomplished like that:
def reverse_a_string(my_text):
return my_text[::-1]
now you can do something like that:
s = raw_input("Please enter a string to be reversed\n") #input in Python3
r = reverse_a_string(s)
print r
r will contain the reversed value of s, and will be printed.
About your second function - well, I assume that based on this answer you can make it yourself, but comment me if you need assistance with the second one.
Local variables
About your 3rd example:
def reverse_a_string(string):
string = "Hello"
reverse = string[::-1]
print(reverse)
This is something that is really worth delaying and understanding.
the variable reverse is first used inside the function. This makes it a local variable.
This means that the variable is stored in the memory when the function is called, and when it finishes, it is removed. You can say it's lifetime is from when the function is called to when the function is done.
This means that even if you called reverse_a_string(string), you wouln't be able to use the reverse variable outside of the function, because it would be local.
If you do want to pass a value like that, you have to "declare" your variable outside of the function and to use the global keyword, like that:
reverse = "" #This makes reverse a global variable
def reverse_a_string(string):
global reverse #Stating that we are going to use the global variable reverse
reverse = string[::-1]
# Then you can call it like that:
reverse_a_string("Hello")
print reverse
The output will be
olleH
Although it's strongly not recommended to do it in Python, or in any other language.
Once you create a function you must call it. You have created the function reverse_a_string but then you never actually call it. Think about a function as a button that does something everytime it is pushed (or in our case called). If you never push the button then although it has the potential to do something, it never will. In order for the set of instructions to happen we need to push the button (or in our case call the function). So in order for your code to work you first need to define the function then actually call it:
def reverse_a_string():
string="Hello"
reverse = string[::-1]
print reverse
reverse_a_string()
Result: 'olleH'
If you want to pass your own string in to the function so it doesn't just return 'olleH' all the time your code needs to look like such:
def reverse_a_string(stringThatWillBeReversed):
reverse = stringThatWillBeReversed[::-1]
print reverse
reverse_a_string('whateverStringYouWant')
Result: The reverse of the string you entered.
Hope that helps!
I don't know whether you are asking how to define functions in python or something else
If you want to learn python functions, go to http://www.tutorialspoint.com/python/python_functions.htm or just write python tutorial in google, you will get billions of good sites
def reverse_a_string(string):
#function definition
reverse = string[::-1]
print(reverse)
#function call
reverse_a_string("your string")
But you to define function for this, you could simply do
print( string[::-1] )
# defines the 'Reverse a String' function and its arguments
def reverse_a_string():
print(string)
reverse = string[::-1]
print(reverse)
print("Type a string") # asks the user for a string input
string = input() # assigns whatever the user input to the string variable
reverse_a_string() # simply calls the function
for functions, you have to define the function, then simply call it with the function name i.e. funtion()
In my example, I ask for a string, assign that to the variable, and use it within the function. If you just want to print hello (I'm a little unclear from your question) then simply including the print("hello") or w/ variable print(string) will work inside the function as well.
Trying to gain access to this string to test it if it has 3 or more blues "b" inside of it. ---Both test and three_or_more_blues are functions.----- I'm completely lost, any one got an idea? Please change my title if it doesn't fit my question. Not sure really how to ask the question. Thanks!
test(three_or_more_blues, "brrrrrbrrrrrb")
Assuming test is a function that takes a function and a string as paramters, and three_or_more_blues is a function that returns true if its string parameter has 3 or more 'b' characters, then
def test(func, str):
if func(str):
# do something with str
test(three_or_more_blues, "brrrrrbrrrrrb")
You could use .count().
sentence = 'brrrrrbrrrrrb'
amount = sentence.count('b')
print(amount)
And then you could use a loop to calculate your next step.
if (amount >= 3):
# Do something
I am not sure if I understand you correctly - you are asking how to pass the string 'brrrrrbrrrrrb' to the three_or_more_blues function?
If that is the case, than you just simply pass it when you call the three_or_more_blues function like this:
def test(func, some_string):
func(some_string) # here you call the passed function
# if three_or_more_blues would look like this:
def three_or_more_blues(some_string):
print "Yes, 3 or more b's" if some_string.count('b') >= 0 else "No"
# you would get this from your function call
test(three_or_more_blues, "brrrrrbrrrrrb") # prints: "Yes, 3 or more b's"
I am having a problem such as:
def function (number):
for number in list:
number = number + 1
For example function(1):
for number in range(1,5):
number = number + 1
Error come back as "can't assign function call"
I would like to use that variable as a value for further calculations.
Help!
I think you have two problems. First, you are not naming your function or declaring it properly; you should do this:
def f(number):
...
Second, you are naming the function parameter number but on the next line you seem to be treating list as though it were the parameter. I think you mean to do this instead:
def f(list):
for number in my_list:
...
Functions in python are defined using the def keyword:
def function_name(number):
for number in my_list:
number = number + something
you have to use def to define a function