Python-22-file文件读取

打开和关闭文件-open

with可以自动关闭管道

 with open('','r') as fp:
 pass

不用with，需要关闭

 file=open('','r') # 建立管道
 content=file.read() # 读入数据
 file.close() # 关闭管道

文件如果找不到

 #【文件读取，若文件不存在则报错】
 with open('datas/test.txt','rb') as fp:
     data=fp.read()
     print(data)
     data_str=data.decode(encoding='UTF-8')
     print(data_str)
 
 #【文件写入，若文件不存在就新建文件】
 with open('datas/test_input.txt', 'wb') as fp:
     fp.write('写入文件'.encode(encoding='UTF-8'))

open()参数
- filename
- mode：r、w、a、rb、wb、ab
- buffer：为0不缓存，为1缓存，为正是缓存区大小，为负是系统默认的大小
- encoding：utf-8(8为最小位数，即英文一个字节，8bit)

readline和readlines

 #fp自带迭代器
 with open('datas/test.txt','r',encoding='utf-8') as fp:
     #readline()-读一行，为string类型
     while 1:
         line = fp.readline()
         print(line)
         if not line:
             break
 with open('datas/test.txt', 'r', encoding='utf-8') as fp:
     # readlines()-读多行，为list类型
     datas=fp.readlines()
     print(type(datas),datas)

tell()

 fp.tell()--文件光标当前位置，即获取当前文件读取指针的位置

seek()

seek(x,0)：从起始位置往后移动x个字符
seek(x,1)：从当前位置往后移动x个字符
seek(-x,2)：从结尾往前移动x个字符
ps：在文本文件中，没有使用b模式选项打开的文件，只允许从文件头开始计算相对位置，从文件尾计算时就会引发异常。
```
 with open('datas/test.txt', 'r', encoding='utf-8') as fp:
 fp.seek(3,0) # 从开始移动3个字符
 data=fp.read()
 print(data)
 #
 with open('datas/test.txt', 'rb') as fp:
 fp.seek(-3,2)# 从结尾往前移动3个字符
 data=fp.read()
 print(data)
```

json序列化

 users=[{"id":"001","name":"python"},{"id":"002","name":"语言"}]
 import json
 #1.dict->str
 str_users=json.dumps(users,ensure_ascii=True)
 #2.str->dict（序列化）
 json_users=json.loads(str_users,encoding='utf-8')
 
 with open('datas/users.json','w',encoding='UTF-8') as fp:
     json.dump(users,fp,ensure_ascii=True)
 
 with open('datas/users.json','r',encoding='UTF-8') as fp:
     u=json.load(fp)
     print(u[0])

eval()：也可序列化，但一般用法为：

 #1.
 print('1+2')
 print(eval('1+2'))

excel：python读取excel依托于excel软件

openpyxl模块

安装第三方：pip install openpyxl

使用openpyxl读取excel全部表，形成字典列表（从row=1,column=1开始）

def read_excel_allsheet_dictlist_openpyxl():
     '''
     使用openpyxl读取excel全部表，形成字典列表
     :return 字典列表:
     '''
     from openpyxl import Workbook
     from openpyxl import load_workbook
     workbook_=load_workbook(u"datas/test_e.xlsx")
     sheet_names=workbook_.get_sheet_names()
     sheet_list=[]
     for sheeti in sheet_names:
         table=workbook_.get_sheet_by_name(sheeti)
         table_list=[]
         for i in range(2,table.max_row+1):
             table_dict={}
             for j in range(1,table.max_column+1):
                 table_dict[table.cell(row=1,column=j).value]=table.cell(row=i,column=j).value
             table_list.append(table_dict)
         sheet_list.append({sheeti:table_list})
     return sheet_list
 print(read_excel_allsheet_dictlist_openpyxl())

使用openpyxl写入excel表并形成xlsx文件

 def write_excel_list_openpyxl():
     '''
     使用openpyxl将所给列表列表逐行写入excel中
     :return: 
     '''
     from openpyxl import Workbook
     from openpyxl import load_workbook
     from openpyxl.writer.excel import ExcelWriter
     rows=[
         ['Number','data1','data2'],
         [2,40],
         [3,40,25],
         [4,50,30]
     ]
     excel=Workbook()
     sheet=excel.create_sheet('Data',index=1)
     for row in rows:
         sheet.append(row)
     excel.save(r'datas.xlsx')
 write_excel_list_openpyxl()
 
 def write_excel_dictlist_openpyxl():
     '''
     使用openpyxl将所给字典列表转换成列表列表写入excel
     :return: 
     '''
     from openpyxl import Workbook
     from openpyxl import load_workbook
     from openpyxl.writer.excel import ExcelWriter
     from utils.util import uid
     users=[
         {'id': 1.0, 'name': 'iphone', 'price': 12000.0},
         {'id': 2.0, 'name': 'vivo', 'price': 9000.0}
     ]
     rows=[]
     rows.append(list(users[0].keys()))
     for user in users:
         rows.append(list(user.values()))
     excel=Workbook()
     sheet=excel.create_sheet('Data',index=1)
     for row in rows:
         sheet.append(row)
     excel.save(r'{0}.xlsx'.format('datas_'+uid()))
 write_excel_dictlist_openpyxl()

xlrd/xlwt

安装第三方：pip install xlrd pip install xlwt

使用xlrd读取excel全部表，形成字典列表（从row=0，column=0开始）

def read_excel_allsheet_dictlist_xlrd():
      '''
     使用xlrd读取excel全部表，形成字典列表
     :return 字典列表:
     '''
     import xlrd
     workbook_=xlrd.open_workbook(u"datas/test_e.xlsx")
     sheet_names=workbook_.sheet_names()
     sheet_list=[]
     for tablei in sheet_names:
         table=workbook_.sheet_by_name(tablei)
         table_list=[]
         for i in range(1,table.nrows):
             dict={}
             for j in range(table.ncols):
                 dict[table.row_values(0)[j]]=table.row_values(i)[j]
             table_list.append(dict)
         sheet_list.append({tablei:table_list})
     return sheet_list
 print(read_excel_allsheet_dictlist_xlrd())

使用xlwt写入excel表

 def write_excel_list_xlwt():
     '''
     使用xlwt将列表列表写入excel
     :return: 
     '''
     import xlwt
     from utils.util import uid
     rows=[
         ['Number','data1','data2'],
         [2,40],
         [3,40,25],
         [4,50,30]
     ]
     excel=xlwt.Workbook()
     sheet=excel.add_sheet('Data',cell_overwrite_ok=True)
     for i in range(len(rows)):
         for j in range(len(rows[i])):
             sheet.write(i,j,rows[i][j])
     excel.save(r'{0}.xlsx'.format('datas_xlwt_'+uid()))
 write_excel_list_xlwt()

csv

用csv读取csv文件读取为字典列表

 def read_csv_to_dicts(field_names=None):
     import csv
     import json
     from collections import OrderedDict
     with open("datas/athlete_events.csv",'r',encoding='utf-8') as csv_file:
         header_line=csv_file.readline().replace(r'"','')
         headers=header_line.strip().split(',')
     with open('datas/athlete_events.csv','r',encoding='utf-8') as csv_file:
         reader=csv.DictReader(csv_file)
         datas=[]
         for row_dict in reader:
             ordered_row_dict=OrderedDict()
             if field_names:
                 for field in field_names:
                     ordered_row_dict[field]=row_dict[field]
             else:
                 for field in headers:
                     ordered_row_dict[field]=row_dict[field]
             datas.append(dict(ordered_row_dict))
         return datas
 print(read_csv_to_dicts())

用csv写入csv文件

 def writer_csv_dictlist():
     import csv
     users=[
         {'id': 1.0, 'name': 'iphone', 'price': 12000.0},
         {'id': 2.0, 'name': 'vivo', 'price': 9000.0}
     ]
     with open('datas/users2.csv','w') as fp:
         headers=users and list(users[0].keys())
         writer=csv.DictWriter(fp,fieldnames=headers)
         writer.writeheader()
         writer.writerows(users)
 writer_csv_dictlist()

来源：https://blog.csdn.net/qq_38328762/article/details/99072294

标签

openpyxl

table

csv

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