python练习

8阶

FUNDAMENTALS ARRAYS NUMBERS

You get an array of numbers, return the sum of all of the positives ones.
Example [1,-4,7,12] => 1 + 7 + 12 = 20
Note: if there is nothing to sum, the sum is default to 0.

def positive_sum(arr):
    return sum(x for x in arr if x > 0)

sum(iterable[,start])

• iterable -- 可迭代对象，如：列表、元组、集合。
• start -- 指定相加的参数，如果没有设置这个值，默认为0。

Correct the mistakes of the character recognition software

Character recognition software is widely used to digitise printed texts. Thus the texts can be edited, searched and stored on a computer.

When documents (especially pretty old ones written with a typewriter), are digitised character recognition softwares often make mistakes.

Your task is correct the errors in the digitised text. You only have to handle the following mistakes:

• S is misinterpreted as 5
• O is misinterpreted as 0
• I is misinterpreted as 1

The test cases contain numbers only by mistake.

def correct(string):
    return string.translate(str.maketrans("501", "SOI"))

• str.translate(table[, deletechars]);
  _ table -- 翻译表，翻译表是通过maketrans方法转换而来。_
  deletechars -- 字符串中要过滤的字符列表。
• str.maketrans(intab, outtab)
  _ intab -- 字符串中要替代的字符组成的字符串。_
  _ outtab -- 相应的映射字符的字符串。_

def correct(string):
    return string.replace('1','I').replace('0','O').replace('5','S')

• str.replace(old, new[, max])
  _ old -- 将被替换的子字符串。_
  _ new -- 新字符串，用于替换old子字符串。_
  _ max -- 可选字符串, 替换不超过 max 次_

This Kata is intended as a small challenge for my students

All Star Code Challenge #18

Create a function called that accepts 2 string arguments and returns an integer of the count of occurrences the 2nd argument is found in the first one.

If no occurrences can be found, a count of 0 should be returned.

strCount('Hello', 'o') // => 1
strCount('Hello', 'l') // => 2
strCount('', 'z') // => 0

Notes:

• The first argument can be an empty string
• The second string argument will always be of length 1

7阶

A History Lesson

The Pony Express was a mail service operating in the US in 1859-60.
Pony Express
It reduced the time for messages to travel between the Atlantic and Pacific coasts to about 10 days, before it was made obsolete by the transcontinental telegraph.

How it worked
There were a number of stations, where:

The rider switched to a fresh horse and carried on, or
The mail bag was handed over to the next rider
Kata Task
stations is a list/array of distances (miles) from one station to the next along the Pony Express route.

Implement the riders method/function, to return how many riders are necessary to get the mail from one end to the other.

NOTE: Each rider travels as far as he can, but never more than 100 miles.

#form me
def riders(stations):
    count=1
    temp=0
    for x in stations:
        temp+=x
        if temp>100:
            count+=1
            temp=x
    return count

#from others
def riders(A):
    Z=[0]
    for x in A:
        if Z[-1]+x<=100:Z[-1]+=x#z这里是一个简单的判断语句不是三目运算大姐
        else:Z.append(x)
    return len(Z)

**Z[-1]+x<=100:Z[-1]+=x 判断冒号左边，左边满足做右边

Beginner Series #3 Sum of Numbers

Given two integers a and b, which can be positive or negative, find the sum of all the numbers between including them too and return it. If the two numbers are equal return a or b.

Note: a and b are not ordered!

Examples

get_sum(1, 0) == 1 // 1 + 0 = 1
get_sum(1, 2) == 3 // 1 + 2 = 3
get_sum(0, 1) == 1 // 0 + 1 = 1
get_sum(1, 1) == 1 // 1 Since both are same
get_sum(-1, 0) == -1 // -1 + 0 = -1
get_sum(-1, 2) == 2 // -1 + 0 + 1 + 2 = 2

def get_sum(a,b):
    return sum(xrange(min(a,b), max(a,b)+1))

Leonardo numbers

The Leonardo numbers are a sequence of numbers defined by:

L(0) = 1 || 0
L(1) = 1 || 0
L(x) = L(x - 1) + L(x - 2) + 1

Generalizing the above a bit more:

L(x) = L(x - 1) + L(x - 2) + a

Assume a to be the add number.

---

Task

Return the first n Leonardo numbers as an array.

Input

• n : The number of Leonardo numbers to be shown
• L0 : Whether L(0) is 0 or 1
• L1 : Whether L(1) is 0 or 1
• add : The add number

Examples

input : n = 5 , L0 = 1 , L1 = 1 , add = 1
output : [ 1, 1, 3, 5, 9 ]

input : n = 5 , L0 = 0 , L1 = 0 , add = 2
output : [ 0, 0, 2, 4, 8 ]

input : n = 10 , L0 = 0 , L1 = 1 , add = 4
output : [ 0, 1, 5, 10, 19, 33, 56, 93, 153, 250 ]

input : n = 5 , L0 = 0 , L1 = 0 , add = 0
output : [ 0, 0, 0, 0, 0 ]

def L(n, L0, L1, add) :
    Z=[L0,L1]
    for x in range(1,n-1):
        Z.append(L0+L1+add)
        L0,L1=L1,L0+L1+add
    return Z

Introduction and Warm-up (Highly recommended)

Task

Given an array/list [] of integers , Construct a product array Of same size Such That prod[i] is equal to The Product of all the elements of Arr[] except Arr[i].

Notes

• Array/list size is at least 2 .

• Array/list's numbers Will be only Postives

• Repeatition of numbers in the array/list could occur.

---

Input >> Output Examples

1- productArray ({12,20}) ==>  return {20,12}

Explanation**:

• The first element in prod [] array 12 is the product of all array's elements except the first element

• The second element 20 is the product of all array's elements except the second element .

2- productArray ({1,5,2}) ==> return {10,2,5}

Explanation:

• The first element 10 is the product of all array's elements except the first element 1

• The second element 2 is the product of all array's elements except the second element 5

• The Third element 5 is the product of all array's elements except the Third element 2.

3- productArray ({10,3,5,6,2}) return ==> {180,600,360,300,900}

Explanation:

• The first element 180 is the product of all array's elements except the first element 10

• The second element 600 is the product of all array's elements except the second element 3

• The Third element 360 is the product of all array's elements except the third element 5

• The Fourth element 300 is the product of all array's elements except the fourth element 6

• Finally ,The Fifth element 900 is the product of all array's elements except the fifth element

from operator import mul
from functools import reduce

def product_array(numbers):
    tot = reduce(mul,numbers)
    return [tot//n for n in numbers]

• Python reduce() 函数
  描述 reduce() 函数会对参数序列中元素进行累积。函数将一个数据集合（链表，元组等）中的所有数据进行下列操作：用传给 reduce 中的函数 function（有两个参数）先对集合中的第 1、2 个元素进行操作，得到的结果再与第三个数据用 function 函数运算，最后得到一个结果。
  语法 reduce(function, iterable[, initializer])
  参数
• function -- 函数，有两个参数
• iterable -- 可迭代对象
• initializer -- 可选，初始参数
  返回值返回函数计算结果。

** 实例**

以下实例展示了 reduce() 的使用方法：

def add(x, y) : # 两数相加 ...
return x + y
reduce(add, [1,2,3,4,5]) # 计算列表和：1+2+3+4+5
15 >>>
reduce(lambda x, y: x+y, [1,2,3,4,5]) # 使用 lambda 匿名函数

from numpy import prod

def product_array(numbers):
    p = prod(numbers)
    return [p // i for i in numbers]

持续更，未完