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Python: Print the number of prime numbers which are less than or equal to a given integer

Python Basic - 1: Exercise-38 with Solution

Write a Python program to print the number of prime numbers which are less than or equal to a given integer.

Input:
n (1 ≤ n ≤ 999,999)

Sample Solution:

Python Code:

primes = [1] * 500000
primes[0] = 0
 
for i in range(3, 1000, 2):
    if primes[i // 2]:
        primes[(i * i) // 2::i] = [0] * len(primes[(i * i) // 2::i])
 
print("Input the number(n):")
n=int(input())
if n < 4:
    print("Number of prime numbers which are less than or equal to n.:",n - 1)
else:
    print("Number of prime numbers which are less than or equal to n.:",sum(primes[:(n + 1) // 2]) + 1)

Sample Output:

Input the number(n):
 35
Number of prime numbers which are less than or equal to n.: 11

Pictorial Presentation:

Python: Print the number of prime numbers which are less than or equal to a given integer

Flowchart:

Flowchart: Python - Print the number of prime numbers which are less than or equal to an given integer

Python Code Editor:

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Previous: Write a Python program which reads an integer n and find the number of combinations of a,b,c and d (0 ≤ a,b,c,d ≤ 9) where (a + b + c + d) will be equal to n.
Next: Write a program to compute the radius and the central coordinate (x, y) of a circle which is constructed by three given points on the plane surface.

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Python: Tips of the Day

Returns the symmetric difference between two lists, after applying the provided function to each list element of both

Example:

def tips_symmetric_difference_by(p, q, fn):
  _p, _q = set(map(fn, p)), set(map(fn, q))
  return [item for item in p if fn(item) not in _q] + [item for item in q if fn(item) not in _p]
from math import floor
print(tips_symmetric_difference_by([4.2, 2.4], [4.6, 6.8],floor))

Output:

[2.4, 6.8]