谁能告诉我为什么我的程序可以在Python2.7而不是3.3中运行？

Question

我有这两个函数：

def MatchRNA(RNA, start1, end1, start2, end2):
    Subsequence1 = RNA[start1:end1+1]
    if start1 > end1:
        Subsequence1 = RNA[start1:end1-1:-1]
    Subsequence2 = RNA[start2:end2+1]
    if start2 > end2:
        Subsequence2 = RNA[start2:end2-1:-1]
    return Subsequence1, Subsequence2


def main():
    RNA_1_list = ['A','U','G','U','G','G','G','U','C','C','A','C','G','A','C','U','C','G','U','C','G','U','C','U','A','C','U','A','G','A']
    RNA_2_list = ['C','U','G','A','C','G','A','C','U','A','U','A','A','G','G','G','U','C','A','A','G','C']
    RNA_Values = {'A': 1, 'U': 2, 'C': 3, 'G': 4}
    RNA1 = []
    RNA2 = []
    for i in RNA_1_list:
        if i in RNA_Values:
            RNA1.append(RNA_Values[i])
    for i in RNA_2_list:
        if i in RNA_Values:
            RNA2.append(RNA_Values[i])
    RNA = list(input("Which strand of RNA (RNA1 or RNA2) are you sequencing? "))       
    Start1, End1, Start2, End2 = eval(input("What are the start and end values (Start1, End1, Start2, End2) for the subsequences of the strand? "))
    Sub1, Sub2 = MatchRNA(RNA, Start1, End1, Start2, End2)
    print(Sub1)
    print(Sub2)

因此，当我运行主函数，并输入(例如)：RNA1，然后是3、14、17、28，它应该打印两个列表：[2,4,4,4,2,3,3,1,3,4,1,3]和[4,2,3,4,2,3,2,1,3,2,1,4]。当我测试这段代码时，我无意中使用了Python2.7，它工作得很好(没有那个eval )，但是当我在3.3中运行它(并把eval放回去)时，它打印了两个列表，'1‘和[]。有没有人知道为什么它在3.3中不能工作，或者我如何让它在3.3中工作？提前谢谢。

Answer 1

在Python3中，input()返回一个字符串，而在Python2中，它等同于eval(raw_input)。

对于RNA1作为输入：

Python3:

>>> RNA1 = []
>>> list(input("Which strand of RNA (RNA1 or RNA2) are you sequencing? "))
Which strand of RNA (RNA1 or RNA2) are you sequencing? RNA1
['R', 'N', 'A', '1']

Python2:

>>> list(eval(input("Which strand of RNA (RNA1 or RNA2) are you sequencing? ")))
Which strand of RNA (RNA1 or RNA2) are you sequencing? RNA1
[]

Answer 2

很接近，但问题的主要来源在这里：

 RNA = list(input("Which strand of RNA (RNA1 or RNA2) are you sequencing? "))

那里的list()调用在任何情况下都是无用的。

在Python2中，当您输入RNA1时，input()将计算该符号并返回绑定到RNA1的列表。

在Python3中，input()返回字符串"RNA1"，无意义的;-) list()将其转换为

['R', 'N', 'A', '1']

更改代码以在两个版本下运行的一种方法是:首先在顶部添加以下内容：

try:
    raw_input
except:  # Python 3
    raw_input = input

然后更改输入行：

RNA = eval(raw_input("Which strand of RNA (RNA1 or RNA2) are you sequencing? "))
Start1, End1, Start2, End2 = eval(raw_input("What are the start and end values (Start1, End1, Start2, End2) for the subsequences of the strand? "))