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Das Python Praxisbuch
Der große Profi-Leitfaden für Programmierer
Farid Hajji
Addison Wesley / Pearson Education
ISBN 978-3-8273-2543-3 (Sep 2008), 1298 Seiten.

4. Zahlen

Die Grundzahlentypen

Screenshots:

Dezimalzahlen mit dem decimal-Modul

Screenshots:

#!/usr/bin/env python
# decimal_localcontext.py -- compute with specific precision

from __future__ import with_statement

import decimal

def sumprec(prec=6, arglist=[]):
    "Compute the sum of list arglist with precision prec."
    with decimal.localcontext() as lctx:
        # Here, computations should occur with precision prec
        lctx.prec = prec
        result = decimal.Decimal("0")
        for num in arglist:
            result = result + decimal.Decimal(num)
    # Resume computation with default or previous precision
    return result

if __name__ == '__main__':
    import sys
    if len(sys.argv) < 2:
        print "Usage:", sys.argv[0], "precision [num1 [num2 ...]]"
        sys.exit(1)
    print sumprec(int(sys.argv[1]), sys.argv[2:])

decimal_localcontext

Zufallszahlen mit dem random-Modul

Zufallszahlen mit dem Mersenne Twister

#!/usr/bin/env python
# get_sample_naive.py -- Get a random sample from a population. Naive version.

import random

def get_sample_naive(population, size):
    "Return a list of size random elements from the list population."
    population_size = len(population)
    result = []
    i = 0
    while (i < size):
        idx = random.randrange(0, population_size)
        result.append(population[idx])
        i = i + 1
    return result

if __name__ == '__main__':
    print get_sample_naive(['apples', 'oranges', 'lemons', 'bananas'], 3)

get_sample_naive.py

Zusammenfassung