I am a beginner in Python and I was trying to write a small program that asks the user to enter an integer that is greater than 0. The function should keep on asking the user for the number until it is valid.
I tried something like below, however I am getting the wrong results. Can you please help me understand my error?
num = input('please enter a number: ' )
n = int(num)
while n < 0:
num = input('please enter a number: ' )
if n >= 0:
print('Valid number')
else:
print('Invalid number')
Is it possible to start the code without an input function? (like to start with num = int())
Thank You for Your Time
There's an error with the logic behind your code.
You firstly ask the user for a number and if he inputs a number which is greater than or equal to 0, the while-loop will never start (in your script: while n < 0:), which, I assume is fine, because the goal of your program is, as you said, to make "the user to enter an integer that is greater than 0".
If the user inputs a number that is smaller than or equal to 0, the while-loop will start, but will never break because inside of it, the value of variable n never changes, only does the value of num.
This is an appropriate script considering that you want to make the user input a number greater than 0, and that you want to give feedback regarding their input.
n = None
while n <= 0:
n = int(input('please enter a number: '))
if n <= 0:
print('Invalid number')
else:
pass # the loop will break at this point
# because n <= 0 is False
print('Valid number')
The code has the user stuck in a loop until they write a number that's greater than 0.
Another solution would be to, inside the loop, check whether int(num) is greater than 0 and if it is, print 'Valid number' and do break to stop the loop; if it's not, print 'Invalid number' (though then the loop doesn't need to be defined by while n < 0:; rather by while True:.
Also, what do you mean by this:
Is it possible to start the code without an input function? (like to start with num = int())
Please clarify this part.
If your problem is the code not terminating, writing Invalid number all the time it's because you are not updating the value of n. You assigned it just once. The solution to your problem is as follows:
n = -1
while n < 0:
n = int(input('please enter a number: '))
if n >= 0:
print('Valid number')
else:
print('Invalid number')
By the way you get rid of starting the code without an input function.
Edit:
As you just said - you want to keep the input reading despite passing an negative integer into the command line. This should help you accomplish this:
while True:
n = int(input('please enter a number: '))
if n >= 0:
print('Valid number')
else:
print('Invalid number')
This loop will go forever until you exit the program lets say with ctrl + C. while True: is as you see an forever ongoing loop, because the True argument will never be false.
Related
as you can see down it's not giving the value of input to the if! why? and how i can make the value of input be stored to Variable (number)
number = input(f"Enter a Number? ")
if number == (1):
print("one")
if number == (2):
print("two or greater")
else:
print("negative number")
Enter a Number? 1
negative number
There are some issues, usually when you use input and expect a number to be submitted, you want to use int() before it to make sure the input is understood as a number (type int). Furthemore, when you want to state an "else-if" statement you should use elif. Finally, the parenthesis are not necessary in your if statement. The following should work:
number = int(input("Enter a Number? "))
if number == 1:
print("one")
elif number >= 2: #I've changed this syntax, because two or greater is written like this
print("two or greater")
else:
print("negative number")
Here is the output I'm trying:
Enter a Number? 3
two or greater
I have ran into some problems while trying to combine while loop and ValueError.
Initially I wanted my program to add numbers together. When the sum of numbers has exceeded X, I would like my program to continue to else statement. At first I didn't focus on the fact that input could also be (for example) string.
number = 1
while number < 10:
add = int(raw_input("Enter a number to add: "))
number += add
print number
else:
print "Number is greater than 10"
I tried combining the first code with try/except and ValueError to accept integers as the only inputs. Second code will not continue to else statement when sum of numbers exceeds X. Could someone please explain why this is not working?
number = 1
while number < 10:
while True:
try:
add = int(raw_input("Enter a number: "))
number += add
print number
except ValueError:
print "Please enter a number"
else:
print "Number is greater than 10"
Thank You.
there's an extra while True: loop resulting in an infinte loop.
Remove it and your code will work fine.
Another example where while(condition) (with condition not True) leads to mistakes: you have to ensure that the loop will be entered once, sometimes by initalizing your condition artificially. I would write that instead
number = 1
while True:
try:
add = int(raw_input("Enter a number: "))
number += add
print number
if number>10:
break
except ValueError:
print "Please enter a number"
print "Number is greater than 10"
I tried to make a guess the number game in python but whenever I guess it repeats 4 times 'your guess is too low'
import random
number = random.randint(1, 20)
guessestaken = 0
print('I am thinking of a number between 1 and 20 ')
guess = raw_input('Take a guess and hit enter')
while guessestaken < 4:
guessestaken = guessestaken + 1
if guess > number:
print('your number is too low')
if guess < number:
print('your number is too high ')
if guess == number:
break
print('well done the number was ' + number + ' and you got it in ' + guessestaken + '')
You are asking for the user input before the while loop.
guess = int(raw_input('Take a guess and hit enter'))
This statement should come within the while block.
The function raw_input returns a string, you should convert it to an integer. You can read more about it in the Documentation.
You need to ask the user for input inside your loop, otherwise you are just comparing his first guess multiple times. Also, you should convert the input value to an integer, because raw_input returns a string.
>>> guess = raw_input('guess the number> ')
>>> type(guess)
<type 'str'>
>>> type(int(guess))
<type 'int'>
You are asking for the input from the user only once, right before you enter your loop. You will need to ask the user for a new input after every iteration of the loop, otherwise the guess will never change!
Additionally, when you read in some input from the user with raw_input it will be a string. You will need to cast it to an int.
Next, if you have a break in your loop, the statements after it will not get called. This means that you need to move the break statement to after the output when the user gets the right answer, or nothing will be printed.
Lastly, your logic in the if statements is backwards, if the guess is less than your generated number then the guess was too low, not too high! Altogether you get:
import random
number = random.randint(1, 20)
guessestaken = 0
print('I am thinking of a number between 1 and 20 ')
while guessestaken < 4:
guess = int(raw_input('Take a guess and hit enter'))
guessestaken = guessestaken + 1
if guess < number:
print('your number is too low')
if guess > number:
print('your number is too high ')
if guess == number:
print('well done the number was ' + number + ' and you got it in ' + guessestaken + '')
break
from random import randint
print("you wanna guess a number between A to B and time of guess:")
A = int(input("A:"))
B = int(input("B:"))
time = int(input("time:"))
x = randint(1, 10)
print(x)
while time != 0:
num = int(input("Enter: "))
time -= 1
if num == x:
print("BLA BLA BLA")
break
print("NOPE !")
if time == 0:
print("game over")
break
You just tried to make a loop in >4 so it is a normal error just to use while True: and change the raw_input to int(raw_input)
import random
number = random.randint(1, 20)
guessestaken = 0
print('I am thinking of a number between 1 and 20 ')
guess = int(raw_input('Take a guess and hit enter'))#make your input a int
while True:#change <4 for True
guessestaken = guessestaken + 1
if guess > number:
print('your number is too low')
if guess < number:
print('your number is too high ')
if guess == number:
break
print('well done the number was ' + number + ' and you got it in ' + guessestaken + '')
I can't seem to get my while loop code to run inside my code. I bet it is very obvious but I cannot seem to find the answer for it. This program is supposed to let you choose how many numbers you want to have randomly chosen and the numbers it can be between. It seems that the while loop doesn't want to work. It skips the while loop and goes to the sleep(10). Thank you for the help!
import random
import time
from time import sleep
x = raw_input("Enter first number you want to be the minimum: ")
y = raw_input("Enter second number you want to be the maximum: ")
a = raw_input("Enter ammount of random numbers you want: ")
p = 1
while p >= a:
print "Your number is " + str(int(random.randint(x - 1,y + 1)))
p = p + 1
sleep(10)
raw_input returns a string. This means you are comparing a string to an integer for your while condition. A quick test shows integers are always "less than" strings.
>>> 10000 > '1'
False
>>> 10000 < '1'
True
Luckily, this behavior is changed in python3 where it throws a TypeError.
Hello I am fairly new to python and would like to know where my program is failing and why.. thanks, the basic coding is as follows,
grade = 0
total = 0
scorecount = 0
while grade >=0:
grade = raw_input("enter grade ->")
grade = int(grade)
total = total + grade
total = int(total)
scorecount = scorecount + 1
scorecount= int(scorecount)
average = total/scorecount
print average
You accept the grade, then add it to the average even if it is -1, since you don't check for -1 until the loop starts again.
To quit a loop halfway through, use break. Then, you can write
while True: # loop 'forever' until break
grade = raw_input("enter grade ->")
grade = int(grade)
if grade == -1:
break # we're done
# rest of processing...
Your checking for -1 AFTER you change it, so you should check that the raw grade is that and break from the loop before processing.
It'd be smarter to use a list to manage something like this.
grades = []
while True:
grade = int(raw_input('Enter a grade: '))
if grade < 0:
break
grades.append(grade)
print '\nAverage:', float(sum(grades)) / len(grades)
There are better ways to have the user break the loop than entering a negative grade, but there you go.