I am new to python programming. Why does this code does not work?
# Print out 2,5,8,11 using `for` loop and `range()`.
for x in range (2,12):
print (x)
x=x+3
I know the following will make the program work
# Print out 2,5,8,11 using `for` loop and `range()`.
for x in range (2,12,3):
print (x)
But I can't understand why the first one doesn't give the desired result whereas the equivalent code would work in C++/C.
Even you try to increment x as x=x+3, it is being changed in every iteration, and take the new value from 2 to 12, depending upon how many iteration has been progressed( if the loop is in 4th cycle, then x will be updated as 4 at the start of the 4th cycle). Even if you've placed x=x+3before the print statement, what it will do is simply printing "iteration + 3"
for x in range (2,12):
print (x)
x=x+3
So this code will produce an output like this;
5
6
7
8
9
10
11
12
13
14
So, there is no way to update x and then use this updated version in next iteration when you are using a for loop in Python.
You cannot increment the value of x when using range() function. There are two ways you can get your desired output.
First Method :
print [x for x in range(2,12,3)]
Second Method :
for x in range(2,12, 3):
print(x)
Related
I'm doing a quiz on sololearn and I'm confused, it says I have to loop from 5 to 1 when I use hint I get this code and when I run the code it becomes infinite loop instead of looping from 5 to 1
is it an infinite looping?
x = 5
while x > 0:
print(x)
x -= 1
Python is sensitive to the indenting of code. In order for your decrement statement to fall within the loop it must be indented to fall under the print statement.
This question already has answers here:
How to remove items from a list while iterating?
(25 answers)
Closed 1 year ago.
data = [1, 2, 3, 4, 5]
for x in data:
print(x)
if data.count(x) < 2:
data.remove(x)
Hello Guys,
so I am currently working through py.checkio.org and am at a point where I have to remove all the numbers that are unique in a list.
When I run my code without the if statement I get an output counting from 1 to 5. But once I run the for loop with the if statement the for loop only runs through the data for every second number and my output is 1 3 5. Can anyone please tell me what is happening here?
While the from #Stef and #0x5453 are both relevant to your problem. The comment from #ConnorTJ is patently wrong. The remove function does not remove the item at the index but the first occurrence of the item.
To answer your question, about what's going on here, let[s examine your code:
The first pass through the value of x is 1
You print the value of x
You then test to see if the number of occurrences of x is less than 2
Since the answer is yes, you proceed to remove the item from the list.
The second pass through the list the For loop picks up the next value in the list (at index 1) which is now the value 3
You print the value 3
You check to see if the count of 3 is less than 2
Since the count is less you remove that item from the list.
This process than continues
Simple solution, use filter()
Construct an iterator from those elements of iterable for which function returns true
it returns a list of the list items that the function returned true for.
example:
x = [1,1,2,2,3,4]
x = filter(lambda f: (x.count(f)<2), x)
x = list(x)
print(x)
or in short: print(list(filter(lambda f: (x.count(f)>=2),x)))
output is [1,1,2,2]
I'm new to programming, and I don't understand why this code returns the binary number of the input.
x = int(input())
while x > 0:
print(x % 2, end='')
x = x // 2
For example, when I enter 6, I expect it to return 0 (6 % 2 = 0, 0 // 2 = 0), but it returns 011.
I stated contemplating this because, in an assignment, we're supposed to use this coding to help us reverse the output (while using a string) but I don't know how to reverse it when I don't know why it works.
The answer of 011 is correct for your code, just trace it thru. You start with 6%2 so you get a 0. Then 6 floor 2 is 3, which is then the x for the next iteration so it becomes 3%2 which is 1 and the final iteration creates the last 1. Remember that you're not changing the value of x in the print statement, it only changes in the last line.
I am programming a program that will make a list of all numbers from 1 to 200 that:
are not divisible by 7 or 11
do not contain the digit 7 or 11 in their number.
I want to use the pass function so when the condition is not met, it will continue with the next number. I don't really know how to do it. The pass function is probably the wrong one. I know the break function does also not work because it will end the whole loop.
Please explain me how to make this program work on this way. There are probably plenty other ways to calculate this, but the point is that i want to understand how to use the for loops better :).
n = 200 #all digits till and including 200
numbers = [] #empty list for accumulation values
for i in range(1,(n+1)):
if i%7 == 0 or i%11 == 0: #if one of these 3 conditions are met
pass #it should continue to the next number (i)
if str(7) in str(i):
pass
if str(11) in str(i):
pass
numbers.append(i)
print(numbers)
print(sum(numbers)) # for my assignment i need to sum the list
use continue in place of pass.
pass does nothing
continue skips to the next loop
so i had to use continue in my example.
I am a novice trying to learn python from Automate The Boring Stuff with Python by Al Sweigart and I came across his block of code to answer a math problem: "What is the sum of all the numbers from 0 to 100?" Apparently, this was a question Gauss got when his teacher wanted to keep him busy.
Sweigart used a for loop and range() function to get the answer:
total = 0
for num in range(101):
total=total+num
print(total)
A page later he states that "you can actually use a while loop to do the same thing as a for loop; for loops are more concise."
How would this statement be rendered in a while loop?
I tried replacing the for with while but got an error: "name 'num' is not defined." I also tried to set up a summation math equation using another block of code from another forum, but completely got lost.
print('Gauss was presented with a math problem: add up all the numbers from 0 to 100. What was the total?')
a=[1,2,3,4,5,...,100]
i=0
while i< len(a)-1:
result=(a[i]+a[i+1])/2
print(result)
i +=1
Then, I tried to setup i in an equation that would loop until each number was added, but got stuck.
print('Gauss was presented with a math problem: add up all the numbers from 0 to 100. What was the total?')
i=0
while i<101:
i=i+1
a=i
Would the while statement be too complex to warrant the effort?
Your last example comes close.
A for loop of this form:
for x in range(N):
# ...
can be replaced by a while loop like this:
x = 0
while x < N:
# ...
x += 1 # equivalent to x = x + 1
Just make sure you leave the rest of the code unchanged!
The for loop is more concise. Notice how we need a "counter" variable , in this case i with the while loop. That's not to say we don't need them in a for loop, however they're integrated nicely into the syntax to make for cleaner code.
i = 0
total = 0
while i < 101:
total += i
i += 1
print(total)
Python's for loop syntax is also a foreach equivalent:
for eachItem in list:
# Do something