Python3查找指定字符串在文件中的行数位置并输出

#! /usr/local/bin/python3
# -*- coding:UTF-8 -*-


import os

# 确定当前操作系统路径分隔符
def path():
    global pathSeparator
    osName = os.name
    if osName == "posix":
        pathSeparator = "/"
    elif osName == "nt":
        pathSeparator = "\\"


# 主程序
def main():
    cwd = os.getcwd()+pathSeparator
    print("\n当前绝对路径: "+cwd)
    filePath = input("输入文件相对或绝对路径(输入q退出): ")
    if filePath == 'q':
        exit()

    # 判断是否绝对路径.如果否,转换为绝对路径
    while not(os.path.isabs(filePath)):
        filePath = cwd+filePath
        # 判断路径是否存在.如果否,重新输入
        while not(os.path.exists(filePath)):
            filePath = input("文件未找到.\n\
                            请重新输入文件路径: ")
            # 判断路径是否文件.如果否,重新输入
            while not(os.path.isfile(filePath)):
                filePath = input("输入的路径不是文件.\n请重新输入文件路径: ")

    string = input("输入要查找的字符串: ")
    print()

    # 开始查找
    count = 0
    f = open(filePath, "r")
    for line in f.readlines():
        if string in line:
            print("第 "+str(count)+" 行已找到.")
            print("该行内容: \n"+line)
        count += 1
    f.close()

if __name__ == "__main__":
    path()
    while True:
        main()