python DataFrame 读取excel文件的前n行

 

def read_head_xls(file,nrow):
    '''
    读取nrow行excel数据,并计算耗时
    用于读取测试数据
    依赖于
    from time import time
    from xlrd import open_workbook
    from pandas import DataFrame
    问题
    空值不能被识别
    '''
    t_start=time()
    wb = open_workbook(file)
    sheet = wb.sheets()[0] #只读活动页
    for i in range(nrow+1):
        if i == 0:
            hed = sheet.row_values(i)
            del i
            break
    dat=DataFrame()
    # del hed
    for i in range(nrow+1):
        if i == 0:
            hed = sheet.row_values(i)
            continue
        t_str = DataFrame(sheet.row_values(i)).T
        dat=dat.append(t_str,ignore_index=True)
        del t_str
    del i  
    del wb
    dat.columns=hed
    del hed
    t_end=time()
    t_cost=t_end-t_start
    print('耗时%0.3f秒钟'%t_cost)
    del t_end,t_start,t_cost
    return dat