Python Challenges: Find the 1000th prime number
Python Challenges - 1: Exercise-39 with Solution
Write a python program to find the 1000th prime number.
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. By Euclid's theorem, there are an infinite number of prime numbers. Subsets of the prime numbers may be generated with various formulas for primes. The first twenty prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71.
Sample Solution:-
Python Code:
def eratosthenes():
D = {}
q = 2
while 1:
if q not in D:
yield q
D[q*q] = [q]
else:
for p in D[q]:
D.setdefault(p+q,[]).append(p)
del D[q]
q += 1
def nth_prime(n):
for i, prime in enumerate(eratosthenes()):
if i == n - 1:
return prime
print(nth_prime(1000))
Sample Output:
7919
Flowchart:
Python Code Editor:
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Python: Tips of the Day
Find current directory and file's directory:
To get the full path to the directory a Python file is contained in, write this in that file:
import os dir_path = os.path.dirname(os.path.realpath(__file__))
(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)
To get the current working directory use
import os cwd = os.getcwd()
Documentation references for the modules, constants and functions used above:
- The os and os.path modules.
- The __file__ constant
- os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
- os.path.dirname(path) (returns "the directory name of pathname path")
- os.getcwd() (returns "a string representing the current working directory")
- os.chdir(path) ("change the current working directory to path")
Ref: https://bit.ly/3fy0R6m
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