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13 December 2020
4 February 2016
Python How to empty a list
Say you have a list in your program and you are going to reuse the name of the list, or delete all items from the list (empty the list). One option is to delete the list completely along with the name :
>>> del li
Another option is to delete all items inside the list:
>>> del li[:]
Many of you can think of another alternative :
>>> li = []
Though li = [], apparently it makes li empty, actually it is creating a new list object and the previous object will be in memory.Now,...
Python AttributeError: 'module' object has no attribute
Are you getting this type of error in your Python program?
AttributeError: 'module' object has no attribute 'whatever' ?
Well, then you might need to change the name of your python file.For example, save the following code in a file named json.py :
import json
print json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
Then try to run it, and you will get this error :
$ python json.py
Traceback (most recent call last):
File "json.py", line 1, in
import json
File "/home/work/practice/json.py",...
Python pow() function returns float or integer?
Today, someone posted this code and asked why x is float ?
>>> from math import pow
>>> x = pow(5, 2)
>>> x
25.0
It's float because the pow function of math package returns float. But there is a built-in pow function in Python which will return integer in this case. You need to restart the python interpreter before you run the following code :
>>> a = 5
>>> x = pow(a, 2)
>>> x
25
>>> type(x)
<type 'int'>
So, don't get confused.&nb...
finding maximum element of a list - divide and conquer approach
Here I share my Python implementation of divide and conquer approach of finding maximum element from a list :"""
Divide and conquer approach to find the maximum from a list
"""
def find_max(li, left, right):
if left == right:
return li[left]
mid = (left + right) / 2
max1 = find_max(li, left, mid)
max2 = find_max(li, mid+1, right)
return max1 if max1 > max2 else max2
def main():
li = [1, 5, 2, 9, 3, 7, 5, 2, 10]
print "Maximum element of the list is", find_max(li, 0, len(li)-1)
...
Python crawler controller
I work on a project where I have written 20+ crawlers and the crawlers are running 24/7 (with good amount of sleep). Sometimes, I need to update / restart the server. Then I have to start all the crawlers again. So, I have written a script that will control all the crawlers. It will first check if the crawler is already running, and if not, then it will start the crawler and the crawler will run in the background. I also saved the pid of all the crawlers in a text file so that I can kill a particular crawler immediately...
Prime Number Generator in Python using Sieve Method
I have implemented a prime number generator in Python using Sieve of Eratosthenes. Here is my code:import math
high = 10000
root = int(math.sqrt(high) + 1.0)
ara = [x % 2 for x in xrange(0, high)]
ara[1] = 0
ara[2] = 1
x = 3
while x <= root:
if ara[x]:
z = x * x
while z < high:
ara[z] = 0
z += (x + x)
x += 2
prime = [x for x in xrange(2, len(ara)) if ara[x] == 1]
print prime
I am looking for ideas to make my code faster....
How to get image size from url
Today I needed to get image size (width and height) from image urls. I am sharing my python code here.
import requests
from PIL import Image
from io import BytesIO
def get_image_size(url):
data = requests.get(url).content
im = Image.open(BytesIO(data))
return im.size
if __name__ == "__main__":
url = "https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcw6adFki0Rnm_aA1YNYXwLWCTzPKjLbG9hI0QweVAoLlNWzK2NQHez4RMhvh9A6WS1eSccU5Swsk2bewxXa9j0rYO3Gl7Jw8ht45n72SONTlwdALyDYJqWtcsW0IY6HFTmFjDuV1yvsRF/s1600/sbn_pic_2.jpg"
...
Code School Python Courses
As Python is getting more and more popular and becoming the de facto standard for starting to learn programming, we can see increasing amount of online content to learn Python. Last week got an email form Code School team to check out their couple of new Python courses. I spent around 30 minutes watching the videos, checkout out the exercises. The exercises are good, and can be done online. They also prepared the videos with care. But one thing that bothers me, the lecture is kind of robotic. I didn't feel anything special,...
9 December 2014
Find rank of matrix using SR modulus Method
Find
rank of matrix using SR modulus Method:
In engineering mathematics it is not easy to find rank of
matrices. SR Modulus method give us flexibility and easy way to find rank of matrices. This method
is working under the project “LOCO POCO
SOCO”, developing by S.K. Chakravarti since 2009.
SR
Modulus method:
If a matrix A=a b cd e fg h i
,
then find the prime modulus of...