如何解决Python中‘No module named cryptography’报错问题

问题场景 #

运行Python连接MySQL的程序时，系统提示需要cryptography包用于SHA256密码处理，但添加import cryptography语句后，出现no module named cryptography错误，且已执行过pip install cryptography安装命令。

解决方案 #

• 检查Python环境与pip的对应关系
  系统中存在多个Python版本时，pip安装的包可能不在当前运行的Python环境中。

  • 执行which python（Linux/macOS）或where python（Windows），查看当前运行的Python路径；
  • 执行which pip（Linux/macOS）或where pip（Windows），查看pip对应的路径，确保两者一致；
  • 若不一致，使用对应版本的pip重新安装：python3 -m pip install cryptography（Linux/macOS）或py -3 -m pip install cryptography（Windows）。

• 强制重新安装cryptography
  若安装过程中文件损坏，执行pip install --force-reinstall cryptography重新安装包。

• 检查虚拟环境（若使用）
  若代码在虚拟环境中运行，需激活虚拟环境后再安装包，或直接使用虚拟环境内的pip：

  • Linux/macOS：venv/bin/pip install cryptography
  • Windows：venv\Scripts\pip install cryptography

• 验证安装结果
  打开Python交互环境，输入import cryptography，无报错则说明安装成功；也可执行pip list查看已安装包列表，确认cryptography存在。

额外代码问题提示 #

你的代码中insert语句存在参数不匹配问题：

cur.execute("insert into student_register (f_name,l_name,email,question,answer,password) values(%s,%s,%s,%s,%s,%s)",
            (
                self.username_txt.get(),
                self.password_txt.get()
            ))

SQL语句需要6个参数，但仅传入2个，运行时会触发错误，需补充对应字段的参数。

用户原始代码 #

from tkinter import *
from tkinter import ttk, messagebox
import pymysql, os
import credentials as cr
import hashlib
import cryptography


class SignUp:
    def __init__(self, root):
        self.window = root
        self.window.title("Sign Up")
        self.window.geometry("1280x800+0+0")
        self.window.config(bg = "white")

        frame = Frame(self.window, bg="white")
        frame.place(x=350,y=100,width=500,height=550)

        title1 = Label(frame, text="Sign Up", font=("times new roman",25,"bold"),bg="white").place(x=20, y=10)
        title2 = Label(frame, text="play with bangtan", font=("times new roman",13),bg="white", fg="gray").place(x=20, y=50)

        self.username_txt = Entry(frame,font=("arial"))
        self.username_txt.place(x=20, y=130, width=200)

        password = Label(frame, text="New password", font=("helvetica", 15 ,"bold") ,bg="white").place(x=20, y=340)

        self.password_txt = Entry(frame,font=("arial"))
        self.password_txt.place(x=20, y=370, width=420)

        self.signup = Button(frame, text="Sign Up", command=self.signup_func, font=("times new roman", 18, "bold"),
                          bd=0, cursor="hand2", bg="green2", fg="white").place(x=120, y=470, width=250)

    def signup_func(self):
        if self.username_txt.get()==""  or self.password_txt.get() == "":
            messagebox.showerror("Error!","Sorry!, All fields are required",parent=self.window)
        else:
            try:
                connection = pymysql.connect(host="localhost", user='user1', password='root1@11', database="logindata")
                cur = connection.cursor()
                cur.execute("select * from userdata where username_text=%s",self.username_txt.get())
                row=cur.fetchone()

                # Check if th entered email id is already exists or not.
                if row!=None:
                    messagebox.showerror("Error!","The email id is already exists, please try again with another email id",parent=self.window)
                else:
                    cur.execute("insert into student_register (f_name,l_name,email,question,answer,password) values(%s,%s,%s,%s,%s,%s)",
                                    (
                                        self.username_txt.get(),
                                        self.password_txt.get()
                                    ))
                    connection.commit()
                    connection.close()
                    messagebox.showinfo("Congratulations!","Register Successful",parent=self.window)
                    self.reset_fields()
            except Exception as es:
                messagebox.showerror("Error!",f"Error due to {es}",parent=self.window)

    def reset_fields(self):
        self.username_txt.delete(0, END)
        self.password_txt.delete(0, END)

if __name__ == "__main__":
    root = Tk()
    obj = SignUp(root)
    root.mainloop()

内容的提问来源于stack exchange，提问作者chetana