pi_nums.py

converter.py

# -*- coding:utf-8 -*-
#!/usr/bin/python3

import os
import datetime

class PIConverter:
    def __init__(self, maxRead=0, minNum=100000, maxNum=99999999):
        self.maxRead = maxRead
        self.minNum = minNum
        self.maxNum = maxNum
        self.positions = [-1]*(self.maxNum+1-self.minNum)
    
    def convert(self, srcFile, dstFile):
        fsrc = open(srcFile,'r')
        fsrc.read(2)
        try:
            lastStr = ""
            readSize = 1024*8
            currPos = 0
            readed = 0

            starttime = datetime.datetime.now()
            
            offset = len(str(self.minNum)) - 1
            minNumLen = len(str(self.minNum))
            maxNumLen = len(str(self.maxNum))
            if self.maxRead <= 0:
                self.maxRead = os.path.getsize(srcFile)
            if readSize > self.maxRead:
                readSize = self.maxRead

            print("readSize: {}".format(readSize))
            while readed < self.maxRead:
                s = fsrc.read(readSize)
                s = lastStr + s # 这里可以再优化下
                currPos -= len(lastStr)
                for i in range(len(s)-maxNumLen):
                    strLen = minNumLen
                    while strLen <= maxNumLen:
                        subs = s[i:i+strLen]
                        strLen += 1
                        num = int(subs)
                        index = num - self.minNum
                        if self.positions[index] < 0:
                            self.positions[index] = currPos + i
                
                if len(s) == 0:
                    break

                lastStr = s[len(s)-5:]
                currPos += readSize
                readed += readSize
                # if readed % (1024*1024*8) == 0:
                #    print("total read: {}, time used: {}s".format(readed, (datetime.datetime.now() - starttime).seconds))

            print("total read: {}, time used: {}s".format(readed, (datetime.datetime.now() - starttime).seconds))
            # print("done")

            try:
                fdst = open(dstFile,'w+')
                i = 0
                # print(":::", i, self.positions[i])
                for i in range(len(self.positions)):
                    if self.positions[i] >= 0:
                        print("num: {} at {}".format(i+self.minNum, self.positions[i]))
                        fdst.write(str(i)+":"+str(self.positions[i])+"\n")
            finally:
                fdst.close()
        finally:
            fsrc.close()

    def find(self, n):
        if n < self.minNum or n > 99999999:
            return -1
        return self.positions[n - self.minNum]
        
maxRead = 16 # 0则读取整个文件
piConverter = PIConverter(maxRead)

# 把已经统计出来的生成更小的文件
piConverter.convert("./pi-billion.txt", "./pi-position.txt")

# converter 初始化太慢了，所以最好还是先 piConverter.convert 把已经统计出来的生成更小的文件，finder.py 用该文件初始化和做查找
print("piConverter find 141592 at pos:", piConverter.find(141592))
print("piConverter find 415926 at pos:", piConverter.find(415926))

finder.py

# -*- coding:utf-8 -*-
#!/usr/bin/python3

class PIFinder:
    def __init__(self, fname, minNum=100000, maxNum=99999999):
        self.minNum = minNum
        self.maxNum = maxNum
        self.positions = [0]*(self.maxNum+1-self.minNum)
        f = open(fname,'r')
        try:
            for line in f:
                strs = line.split(":")
                i, pos = int(strs[0]), int(strs[1])
                self.positions[i] = pos
        finally:
            f.close()

    def find(self, n):
        if n < self.minNum or n > 99999999:
            return -1
        return self.positions[n - self.minNum]
        
piFinder = PIFinder("./pi-position.txt")
print("piFinder find 141592 at pos:", piFinder.find(141592))
print("piFinder find 415926 at pos:", piFinder.find(415926))

test

python .\converter.py
readSize: 16
total read: 16, time used: 0s
num: 141592 at 0
num: 159265 at 2
num: 265358 at 5
num: 415926 at 1
num: 535897 at 7
num: 592653 at 3
num: 653589 at 6
num: 926535 at 4
num: 1415926 at 0
num: 1592653 at 2
num: 2653589 at 5
num: 4159265 at 1
num: 5358979 at 7
num: 5926535 at 3
num: 6535897 at 6
num: 9265358 at 4
num: 14159265 at 0
num: 15926535 at 2
num: 26535897 at 5
num: 41592653 at 1
num: 53589793 at 7
num: 59265358 at 3
num: 65358979 at 6
num: 92653589 at 4
piConverter find 141592 at pos: 0
piConverter find 415926 at pos: 1

python .\findder.py
piFinder find 141592 at pos: 0
piFinder find 415926 at pos: 1

download pi: https://stuff.mit.edu/afs/sipb/contrib/pi/pi-billion.txt

https://www.v2ex.com/t/814478