创建序列的可能修改列表

I am not very experienced with Python and my script gives the following error:

我对Python不是很有经验，我的脚本会出现以下错误：

"invalid syntax in line 4"

I don't see the reason, maybe someone can help.

我没有看到原因，也许有人可以提供帮助。

I'm trying to create a list of all possible modifications of a sequence ( like SEQWKST). If the letter is "S", the modification would be "phos" . If the letter is "K" there are three possible modifications: "dimeth" "meth" and "ac"

我正在尝试创建一个序列的所有可能修改的列表（如SEQWKST）。如果字母是“S”，则修改将是“phos”。如果字母是“K”，则有三种可能的修改：“dimeth”“meth”和“ac”

I want to create a list with the possible modifications and their positions

我想创建一个包含可能的修改和位置的列表

(eg:
1,phos
4,ac
4,meth
4,meth...)

#!/bin/python

def createPTM (SEQWKST):
    PTMlist = []
    pos = 0
    for N in SEQWKST:
        pos += 1
        if N == "Y":
            PTM = phos
            PTM_list.extend(pos,PTM)
        elif N=="S":
            PTM = phos
            PTMlist.extend(pos,PTM) 
        elif N=="T":
            PTM = phos
            PTMlist.extend(pos,PTM)     
        elif N=="R":
            PTM = meth
            PTM_2 = dimeth
            PTMlist.extend(pos,PTM)
            PTMlist.extend(pos,PTM_2)
        elif N=="K":
            PTM = meth
            PTM_2 = dimeth
            PTM_3 = ac
            PTMlist.extend(pos,PTM)
            PTMlist.extend(pos,PTM_2)
            PTMlist.extend(pos,PTM_3)       
    return PTM_list
    print PTM_list

1 个解决方案

#1

There are, in fact, several problems with your code, but a SyntaxError at line 4 doesn't appear to be one of them.

事实上，您的代码存在一些问题，但第4行的SyntaxError似乎不是其中之一。

Note that extend takes a single argument (a sequence of some kind) and extends a given list with that sequence, so you need to call it with e.g. PTM_list.extend((pos,PTM))

请注意，extend接受一个参数（某种序列）并使用该序列扩展给定列表，因此您需要使用例如PTM_list.extend（（POS，PTM））

You don't define phos, meth, etc, but I'm guessing these are supposed to be string objects?

你没有定义phos，meth等，但我猜这些应该是字符串对象？

You print PTM_list outside your function definition, where it is no longer in scope. I'm guessing you want to print the returned value of create_PTM

您在函数定义之外打印PTM_list，它不再在范围内。我猜你要打印create_PTM的返回值

Try:

尝试：

#!/bin/python

def createPTM (SEQWKST):
    PTM_list = []
    pos = 0
    for N in SEQWKST:
        pos += 1
        if N == "Y":
            PTM = 'phos'
            PTM_list.extend((pos,PTM))
        elif N=="S":
            PTM = 'phos'
            PTM_list.extend((pos,PTM))
        elif N=="T":
            PTM = 'phos'
            PTM_list.extend((pos,PTM))
        elif N=="R":
            PTM = 'meth'
            PTM_2 = 'dimeth'
            PTM_list.extend((pos,PTM))
            PTM_list.extend((pos,PTM_2))
        elif N=="K":
            PTM = 'meth'
            PTM_2 = 'dimeth'
            PTM_3 = 'ac'
            PTM_list.extend((pos,PTM))
            PTM_list.extend((pos,PTM_2))
            PTM_list.extend((pos,PTM_3))
    return PTM_list

print createPTM('YSRKT')

A more Pythonic approach is to use a dictionary instead of if..elif and define a function to do your specialized list extending:

更Pythonic的方法是使用字典而不是if..elif并定义一个函数来进行专门的列表扩展：

#!/bin/python

def createPTM (SEQWKST):
    PTM_list = []

    def extend_PTM_list(pos, PTMs):
        for PTM in PTMs:
            PTM_list.extend((pos, PTM))

    d = {'Y': ['phos'],
         'S': ['phos'],
         'T': ['phos'],
         'R': ['meth', 'dimeth'],
         'K': ['meth', 'dimeth', 'ac']
        }


    for pos, N in enumerate(SEQWKST, start=1):
        extend_PTM_list(pos, d[N])

    return PTM_list

print createPTM('YSRKT')

Output (eg):

输出（例如）：

[1, 'phos', 2, 'phos', 3, 'meth', 3, 'dimeth', 4, 'meth', 4, 'dimeth', 4, 'ac', 5, 'phos']

#1