如何用Python实现一个请销假管理系统

请销假管理系统可以包含以下功能：

1. 登录系统：用户可以输入用户名和密码进行登录，登录成功后可以进入系统。

2. 请假申请：用户可以填写请假申请表，包括请假类型、开始时间、结束时间、请假原因等信息，提交后系统自动发送邮件给审批人。

3. 审批请假：审批人可以查看待审批的请假申请，可以通过或驳回申请，同时可以填写审批意见。

4. 查看请假记录：用户和管理员可以查看已经提交的请假记录，包括请假类型、开始时间、结束时间、请假原因、审批状态等信息。

5. 统计请假情况：管理员可以查看请假统计报表，包括请假类型、请假天数、请假人数等信息。

以下是一个简单的Python代码实现示例：

import smtplib
from email.mime.text import MIMEText

class LeaveApplication:
    def __init__(self, applicant, leave_type, start_date, end_date, reason):
        self.applicant = applicant
        self.leave_type = leave_type
        self.start_date = start_date
        self.end_date = end_date
        self.reason = reason
    
    def submit(self, approver):
        # send email to approver
        subject = f"Leave application from {self.applicant}"
        content = f"Leave type: {self.leave_type}\n" \
                  f"Start date: {self.start_date}\n" \
                  f"End date: {self.end_date}\n" \
                  f"Reason: {self.reason}\n" \
                  f"Please approve or reject this application."
        msg = MIMEText(content)
        msg['Subject'] = subject
        msg['From'] = 'your email address'
        msg['To'] = approver
        s = smtplib.SMTP('your email server address', 25)
        s.login('your email username', 'your email password')
        s.sendmail('your email address', [approver], msg.as_string())
        s.quit()

class LeaveApproval:
    def __init__(self, approver):
        self.approver = approver
        self.applications = []
    
    def approve(self, application):
        application.status = 'approved'
        application.approver = self.approver
        self.applications.append(application)
        # send email to applicant
        subject = f"Leave application approved by {self.approver}"
        content = f"Leave type: {application.leave_type}\n" \
                  f"Start date: {application.start_date}\n" \
                  f"End date: {application.end_date}\n" \
                  f"Reason: {application.reason}\n" \
                  f"Approved by: {self.approver}"
        msg = MIMEText(content)
        msg['Subject'] = subject
        msg['From'] = 'your email address'
        msg['To'] = application.applicant
        s = smtplib.SMTP('your email server address', 25)
        s.login('your email username', 'your email password')
        s.sendmail('your email address', [application.applicant], msg.as_string())
        s.quit()
    
    def reject(self, application):
        application.status = 'rejected'
        application.approver = self.approver
        self.applications.append(application)
        # send email to applicant
        subject = f"Leave application rejected by {self.approver}"
        content = f"Leave type: {application.leave_type}\n" \
                  f"Start date: {application.start_date}\n" \
                  f"End date: {application.end_date}\n" \
                  f"Reason: {application.reason}\n" \
                  f"Rejected by: {self.approver}"
        msg = MIMEText(content)
        msg['Subject'] = subject
        msg['From'] = 'your email address'
        msg['To'] = application.applicant
        s = smtplib.SMTP('your email server address', 25)
        s.login('your email username', 'your email password')
        s.sendmail('your email address', [application.applicant], msg.as_string())
        s.quit()

class LeaveRecord:
    def __init__(self):
        self.records = []
    
    def add_record(self, application):
        self.records.append(application)
    
    def get_records(self):
        return self.records

class LeaveReport:
    def __init__(self, record):
        self.record = record
    
    def get_report(self):
        report = {}
        for application in self.record.get_records():
            if application.status == 'approved':
                leave_type = application.leave_type
                days = (application.end_date - application.start_date).days + 1
                if leave_type in report:
                    report[leave_type] += days
                else:
                    report[leave_type] = days
        return report

这是一个基于面向对象编程的实现示例，其中LeaveApplication类表示请假申请，LeaveApproval类表示请假审批，LeaveRecord类表示请假记录，LeaveReport类表示请假统计报表。

在实际应用中，可以根据需求进行修改和扩展。同时，需要注意安全性和合法性问题，例如用户登录验证、数据校验等。