首頁(yè) 猿問(wèn) 沒有反轉(zhuǎn)功能的反轉(zhuǎn)數(shù)組，但循環(huán)不起作用

沒有反轉(zhuǎn)功能的反轉(zhuǎn)數(shù)組，但循環(huán)不起作用

Python

慕桂英3389331 2023-07-27 16:47:50

因此，我嘗試在不使用反向函數(shù)的情況下從 .txt 文件反轉(zhuǎn)數(shù)組。這就是我所擁有的。numbers = read() #creates numbers array out of the txt filenumbersrev = numbers #blank array for reversenumLength = len(numbers) #measures the length of the arrayprint(numbers)print("Array length of numbers: ", numLength)i = numLengthi = i-1 #since the array starts at 0 instead of 1k = 0for k in range(8): numbersrev[k] = numbers[i] print ("The ", i," element of numbers is the ", k," element of numbersrev") i -= 1 k += 1print(numbersrev)這是我在vscode上調(diào)試后得到的結(jié)果：[2, 4, 9, 11, 8, 3, 2, 5, 10]Array length of numbers: 9The 8 element of numbers is the 0 element of numbersrevThe 7 element of numbers is the 1 element of numbersrevThe 6 element of numbers is the 2 element of numbersrevThe 5 element of numbers is the 3 element of numbersrevThe 4 element of numbers is the 4 element of numbersrevThe 3 element of numbers is the 5 element of numbersrevThe 2 element of numbers is the 6 element of numbersrevThe 1 element of numbers is the 7 element of numbersrev[10, 5, 2, 3, 8, 3, 2, 5, 10]頂部數(shù)組是原始數(shù)組，底部數(shù)組是假定的反轉(zhuǎn)數(shù)組我一生都無(wú)法找出為什么它在中途停止改變numbersrev數(shù)組。有人知道可能是什么原因嗎？

查看完整描述

4 回答

守候你守候我

TA貢獻(xiàn)1802條經(jīng)驗(yàn) 獲得超10個(gè)贊

好吧，有幾件事...

首先，for 循環(huán)在 python 中自動(dòng)增加它們的變量。

所以：

for k in range(8):

...

i -= 1

k += 1

應(yīng)該：

for k in range(8):

...

i -= 1

無(wú)需手動(dòng)增加 k。

接下來(lái)的列表不是數(shù)組。

python 中的列表與 C 等語(yǔ)言中的數(shù)組有很大不同。列表是可變的，并且默認(rèn)情況下通過(guò)引用傳遞。所以當(dāng)你嘗試創(chuàng)建一個(gè)空數(shù)組時(shí)：

numbersrev = numbers #blank array for reverse

您實(shí)際上numbers是從AND引用相同的“列表”numbersrev

你應(yīng)該做的是numbersrev = []

然后在 for 循環(huán)中，只需附加到 numberrev 而不是分配。

for k in range(numLength):

numbersrev.append(numbers[i])

print ("The ", i," element of numbers is the ", k," element of numbersrev")

i -= 1

最后

你可以/應(yīng)該在 for 循環(huán)中引用數(shù)字的長(zhǎng)度而不是硬編碼的值，但是你如何擁有它仍然有效（假設(shè)你只得到8個(gè)數(shù)字）

for k in range(numLength):

...

全部一起

numbers = read() #creates numbers array out of the txt file

numbersrev = [] #blank array for reverse

numLength = len(numbers) #measures the length of the array

print(numbers)

print("Array length of numbers: ", numLength)

i = numLength

i = i-1 #since the array starts at 0 instead of 1

for k in range(numLength):

numbersrev.append(numbers[i])

print ("The ", i," element of numbers is the ", k," element of numbersrev")

i -= 1

print(numbersrev)

反對(duì) 回復(fù) 2023-07-27

慕標(biāo)琳琳

TA貢獻(xiàn)1830條經(jīng)驗(yàn) 獲得超9個(gè)贊

您在這里所做的就是使用以下行將反轉(zhuǎn)數(shù)組指定為普通數(shù)組：

numbersrev = numbers #blank array for reverse

您實(shí)際上對(duì)該循環(huán)所做的事情是這樣的：

numbers[0] = numbers[9] # [10, 2, 3, 4, 5, 6, 7, 8, 9, 10]

numbers[1] = numbers[8] # [10, 9, 3, 4, 5, 6, 7, 8, 9, 10]

numbers[2] = numbers[7] # [10, 9, 8, 4, 5, 6, 7, 8, 9, 10]

numbers[3] = numbers[6] # [10, 9, 8, 7, 5, 6, 7, 8, 9, 10]

numbers[4] = numbers[5] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]

numbers[5] = numbers[4] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]

numbers[6] = numbers[3] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]

numbers[7] = numbers[2] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]

numbers[8] = numbers[1] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]

numbers[9] = numbers[0] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]

...

如果您像這樣分配變量：

numLength = len(numbers) #measures the length of the array

numbersrev = [0]*numLength #blank array for reverse

您將得到正確的答案，因?yàn)榉聪蛄斜聿辉僦赶蛘Ａ斜怼?/p>

反對(duì) 回復(fù) 2023-07-27

慕斯709654

TA貢獻(xiàn)1840條經(jīng)驗(yàn) 獲得超5個(gè)贊

你面臨的問(wèn)題是因?yàn)檫@條線

numbersrev = numbers #blank array for reverse

在這一行中，您不是創(chuàng)建空數(shù)組，而是將numbers數(shù)組的引用保存在名為的新變量中numbersrev。這意味著當(dāng)您在數(shù)組中進(jìn)行操作時(shí)，numbersrev您也會(huì)更改的值numbers。為了避免此類問(wèn)題，您有兩種選擇：

使用切片制作數(shù)組的副本

通過(guò)這種方式，您可以復(fù)制數(shù)組的值，而不是數(shù)組的引用。這意味著您對(duì)新數(shù)組所做的更改不會(huì)更改原始數(shù)組。

numbersrev = numbers[:]

創(chuàng)建一個(gè)空數(shù)組并使用追加而不是賦值

此更改與您所做的略有不同，但基本上您不是創(chuàng)建數(shù)組的副本，而是創(chuàng)建一個(gè)新數(shù)組，該數(shù)組將填充到 for 循環(huán)中，如下所示：

numbers.rev = []

...

for k in range(8):

numbersrev.append(numbers[i])

因此，使用第一個(gè)選項(xiàng)并更改 k 索引中的一些內(nèi)容，我們有這樣的代碼：

numbers = [2, 4, 9, 11, 8, 3, 2, 5, 10] # you can change for read

numbersrev = numbers[:] #copy array elements

numLength = len(numbers) #array length

print(numbers)

print("Array length of numbers: ", numLength)

i = numLength - 1

# you don't need to initialize k because it's initialized and incremented with range in the loop

for k in range(numLength):

numbersrev[k] = numbers[i]

print ("The ", i," element of numbers is the ", k," element of numbersrev")

i -= 1

print(numbersrev)

希望這能幫助你解決問(wèn)題，就像注釋一樣，你可以通過(guò)多種方式解決這個(gè)問(wèn)題：切片（numbers[::-1]）、列表理解和其他一些。所有方法都是有效的，以防萬(wàn)一您想探索更多。

反對(duì) 回復(fù) 2023-07-27

搖曳的薔薇

TA貢獻(xiàn)1793條經(jīng)驗(yàn) 獲得超6個(gè)贊

numbersrev = numbers設(shè)置numbersrev為指向與相同的列表numbers，這意味著當(dāng)您修改numbers或numbersrev同時(shí)修改另一個(gè)列表時(shí)。要制作對(duì)象的實(shí)際副本，您需要調(diào)用numbersrev = numbers.copy(). 另外，@sahasrara62的評(píng)論是正確的，你需要打電話for k in range(numLength)而不是for k in range(8)