Question

我只是在学习编码，所以我决定为自己创建一个项目，创建一个找到抛物线零的函数。我认为我遇到的问题实际上是打印出sqrt。

这是我收到的错误：

File "C:/Users/someb/AppData/Local/Programs/Python/Python37-32/Quadratic Formula Solver revised.py", line 10, in find_zero
    return float(-b) + "+-" + float(math.sqrt(discriminant)) + "/" + float(2 * a)
TypeError: unsupported operand type(s) for +: 'float' and 'str'

这是我的第五次修订版代码，尝试使用不同的方式，这本来应该显示两个不同的答案。

#Real Zero Finder QUadratic Formula
import math
def find_zero(a,b,c):
    discriminant = (b ** 2 - 4 * a * c)
    if discriminant < 0 :
        return "No real Zeros"
    elif discriminant == 0 :
        return "Vertex is the Zero"
    else:
        #This is where the error is taking place
        return float(-b) + "+-" + float(math.sqrt(discriminant)) + "/" + float(2 * a)

def disc(a,b,c):
    return math.sqrt(b ** 2 - 4 * a * c)

Answer 1

您收到此错误，因为Python不知道如何向浮点数添加字符串。您知道您正在尝试将浮点数连接到字符串，但是Python却没有。

在Python 3.6+中打印多个内容的最简单方法是使用格式化的字符串文字（f字符串）：https://docs.python.org/3.6/reference/lexical_analysis.html#f-strings 将f放在字符串之前，然后将想要显示的内容放在花括号{ }内。

return f'{-b} +- {math.sqrt(discriminant)} / {2 * a}'

Answer 2

如上所述，您不能添加字符串和浮点数。由于您似乎正在输出一条消息，因此我更愿意通过将浮点数转换为字符串来解决此问题，然后“ +”将连接这些字符串。这将返回一个字符串，这可能比返回多个值更有用。

return str(-b) + " +- " + str(math.sqrt(discriminant)) + " / " + str(2 * a)

我也取消了float（）转换...我认为他们在这里没有做任何事情。

Answer 3

问题在这里回报：

package a.bogin.revmidterm.Models;

public class StringInfos {

    private int id;
    private String string1;
    private String string2;
    private String string3;

    public StringInfos(String string1, String string2, String string3) {
        this.string1 = string1;
        this.string2 = string2;
        this.string3 = string3;
    }

    public String getString1() {
        return string1;
    }

    public void setString1(String string1) {
        this.string1 = string1;
    }

    public String getString2() {
        return string2;
    }

    public void setString2(String string2) {
        this.string2 = string2;
    }

    public String getString3() {
        return string3;
    }

    public void setString3(String string3) {
        this.string3 = string3;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

}

您正在尝试将package a.bogin.revmidterm; import android.content.Intent; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.support.v7.widget.DividerItemDecoration; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.View; import android.widget.AdapterView; import java.util.ArrayList; import a.bogin.revmidterm.Adapter.StringsAdapter; import a.bogin.revmidterm.DB.DBManager; import a.bogin.revmidterm.Models.StringInfos; public class MainActivity extends AppCompatActivity { ArrayList<StringInfos> listOfAll; StringsAdapter strAdapter; RecyclerView.LayoutManager mLayoutManager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mLayoutManager = new LinearLayoutManager(this); .setLayoutManager(mLayoutManager); RecyclerView myOwnRc = findViewById(R.id.rc); myOwnRc.addItemDecoration(new DividerItemDecoration(getApplicationContext(), DividerItemDecoration.VERTICAL)); mLayoutManager = new LinearLayoutManager(this); myOwnRc.setLayoutManager(mLayoutManager); listOfAll = DBManager.getAllItems(); strAdapter = new StringsAdapter(listOfAll); myOwnRc.setAdapter(strAdapter); myOwnRc.setLayoutManager(new LinearLayoutManager(this)); myOwnRc.setOnItemClickListener(new AdapterView.OnItemClickListener(){ @Override public void onItemClick(AdapterView<?> parent, View v, int pos, long id){ } }); } public void addStuff(View v){ Intent addNew = new Intent(this, AddItem.class); startActivity(addNew); } @Override public boolean onCreateOptionsMenu(Menu menu){ MenuInflater inf = getMenuInflater(); inf.inflate(R.menu.itemsstuff, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item){ switch (item.getItemId()){ case R.id.ea: deleteAll(); return true; case R.id.pref: seePrefs(); return true; default: return super.onOptionsItemSelected(item); } } public void seePrefs(){ } public void deleteAll(){ listOfAll.clear(); finish(); startActivity(getIntent()); } }连接到myOwnRc.setOnItemClickListener(new AdapterView.OnItemClickListener(){ @Override public void onItemClick(AdapterView<?> parent, View v, int pos, long id){ } });，而不要使用加号，而要使用逗号：

return float(-b) + "+-" + float(math.sqrt(discriminant)) + "/" + float(2 * a)

返回函数时显示sqrt

3 个答案: