Python将字符串中的多个位置分别转换为多个字母

如何解决Python将字符串中的多个位置分别转换为多个字母

我正在尝试编写一个python代码，以发现DNA序列内的限制酶位点。限制酶切割特定的DNA序列，但是有些酶并不严格，例如XmnI切割该序列：

GAANNNNTTC

其中N可以是任何核苷酸（A，C，G或T）。如果我的数学是正确的，那就是4 ^ 4 = 256个可以剪切的唯一序列。我想列出这256个短序列，然后对照（较长）输入的DNA序列检查每个短序列。但是，我很难生成256个序列。这是我到目前为止的内容：

cutsequencequery = "GAANNNNTTC"
Nseq = ["A","C","G","T"]
querylist = []
if "N" in cutsequencequery:
    Nlist = [cutsequencequery.replace("N",t) for t in Nseq]
    for j in list(Nlist):
        querylist.append(j)

for i in querylist:
    print(i)
print(len(querylist))

这是输出：

GAAAAAATTC
GAACCCCTTC
GAAGGGGTTC
GAATTTTTTC
4

因此它将每个N切换为A，C，G和T，但是我想我需要另一个循环（或3个）来生成所有256个组合。有没有一种我看不到的有效方法？

解决方法

也许您应该看看python's itertools library，其中包括private static final ObjectMapper MAPPER = Json.mapper(); ，它会为每个可迭代对象的组合创建一个可迭代对象，因此：

import 'dart:async';

import 'package:flutter/material.dart';

class WebScrollbar extends StatefulWidget {
  final Widget child;
  final ScrollController controller;
  final double heightFraction;
  final double width;
  final Color color;
  final Color backgroundColor;
  final bool isAlwaysShown;
  final Function scrollCallBack;
  final double value;

  WebScrollbar({
    this.value,this.scrollCallBack,this.child,this.controller,this.heightFraction = 0.20,this.width = 8,this.color = Colors.black45,this.backgroundColor = Colors.black12,this.isAlwaysShown = false,})  : assert(child != null),assert(controller != null),assert(heightFraction != null &&
            heightFraction < 1.0 &&
            heightFraction > 0.0),assert(width != null),assert(color != null),assert(backgroundColor != null),assert(isAlwaysShown != null);

  @override
  _WebScrollbarState createState() => _WebScrollbarState();
}

class _WebScrollbarState extends State<WebScrollbar> {
  double _scrollPosition = 0;
  bool _isUpdating;
  Timer timer;

  _scrollListener() {
    setState(() {
      _scrollPosition = widget.controller.position.pixels;
    });
  }

  @override
  void initState() {
    widget.controller.addListener(_scrollListener);
    _isUpdating = false;
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    var screenSize = MediaQuery.of(context).size;
    double _scrollerHeight = screenSize.height * widget.heightFraction;

    double _topMargin = widget.controller.hasClients
        ? ((screenSize.height *
                _scrollPosition /
                widget.controller.position.maxScrollExtent) -
            (_scrollerHeight *
                _scrollPosition /
                widget.controller.position.maxScrollExtent))
        : 0;

    return NotificationListener<ScrollNotification>(
      onNotification: (notification) {
        if (notification.depth == 0) {
          if (notification is ScrollUpdateNotification) {
            timer.cancel();
            setState(() {
              _isUpdating = true;
            });
          } else {
            timer = Timer(Duration(seconds: 5),() {
              setState(() {
                _isUpdating = false;
              });
            });
          }
          // print(_isUpdating);
        }
        return true;
      },child: Stack(
        children: [
          widget.child,AnimatedOpacity(
            opacity: widget.isAlwaysShown
                ? 1
                : widget.controller.hasClients
                    ? _isUpdating
                        ? 1
                        : 0
                    : 0,duration: Duration(milliseconds: 900),child: Container(
              alignment: Alignment.centerRight,height: MediaQuery.of(context).size.height,width: 10,margin: EdgeInsets.only(
                left: MediaQuery.of(context).size.width - 10,),color: widget.backgroundColor,child: Align(
                alignment: Alignment.topCenter,child: GestureDetector(
                  child: Container(
                    height: _scrollerHeight,width: widget.width,margin: EdgeInsets.only(
                      left: 1.0,right: 1.0,top: _topMargin,decoration: BoxDecoration(
                      color: widget.color,borderRadius: BorderRadius.all(
                        Radius.circular(3.0),onTapCancel: () {
                    timer = Timer(Duration(seconds: 10),() {
                      setState(() {
                        _isUpdating = false;
                      });
                    });
                  },onTapDown: (details) {
                    timer.cancel();
                    setState(() {
                      _isUpdating = true;
                    });
                  },onVerticalDragUpdate: (dragUpdate) {
                    widget.controller.position
    
    //Say in the line of code below. **The value (3.5)** should be manually set on each page of the app.//
    
                        .moveTo(dragUpdate.globalPosition.dy * 3.5);

                    setState(() {
                      if (dragUpdate.globalPosition.dy >= 0 &&
                          _scrollPosition <=
                              widget.controller.position.maxScrollExtent) {
                        _scrollPosition = dragUpdate.globalPosition.dy +
                            dragUpdate.globalPosition.dy *
                                (_scrollPosition /
                                    widget
                                        .controller.position.maxScrollExtent) -
                            (_scrollerHeight *
                                _scrollPosition /
                                widget.controller.position.maxScrollExtent);
                      }
                    });
                  },],);
  }
}