【Python】文件操作、文件编码方式

一、文件打开、关闭

 

二、with语句自动管理

（不需要自己关）

with open("result.txt","w") as fp:
    with open("test.txt","r") as fp1, open("test1.txt","r") as fp2:
        while True:
            line1 = fp1.readline()
            if line1:
                fp.write(line1)
            else:
                flag = False
                break
            line2 = fp2.readline()
            if line2:
                fp.write(line2)
            else:
                flag = True
                break
        fp3 = fp1 if flag else fp2
        for line in fp3:
            fp.write(line)

 

 （注意短的文件末尾要空一行，不然只用write()，末尾拼接地方会共用一行）

 将read出来的字符串转换成真实python类型：

import json
with open("student_list.txt", "r", encoding='utf-8') as fp:
    data1 = fp.readlines()
    student_list = [eval(each) for each in data1]

print(student_list)

 三、json文件操作

1.任意类型转字符串 json.dumps(),json.loads()

import json 

data1 = json.dumps('3')
print(data1,type(data1))
data1


dict = '{"name": "Tom", "age": 23}'   # 将字符串还原为dict,eval
data2 = json.loads(dict)
print(data2, type(data2))
data2

2.文件操作 json.dump(),json.load() 

import json

information = [
               {'小区名称': '小区A', '均价': 8000, '月交易量': 20},
               {'小区名称': '小区B', '均价': 8500, '月交易量': 35},
               {'小区名称': '小区C', '均价': 7800, '月交易量': 50},
               {'小区名称': '小区D', '均价': 12000, '月交易量': 18}]

with open('房屋信息.json', 'w') as fp:
    json.dump(information, fp, indent=4, separators=(',', ':'))

with open('房屋信息.json') as fp:
    information = json.load(fp)

for info in information:
    print(info)

两种文件load方法：

import json

with open("test2.json", "r", encoding='utf-8') as f:

    data2 = json.loads(f.read())    # load的传入参数为字符串类型
    print(data2, type(data2))

    f.seek(0)                       # 将文件游标移动到文件开头位置

    data3 = json.load(f)
    print(data3, type(data3))

三、csv文件操作

1.读一行

import csv
with open("test.csv", "r") as f:
    reader1 = csv.reader(f)
    rows =[row for row in reader1]
    print(rows)

print(len(rows))
print(rows[0].index('工资'))

"""
读表头，推测阅读器是个迭代器
"""
import csv
with open("test.csv") as f:
    reader = csv.reader(f)
    head_row = next(reader)
    print(head_row)

"""
迭代器性质
"""
import csv
with open("test.csv", "r") as fp:
    reader = csv.reader(fp)
    row1 = [row for row in reader]  # 正常读入
    row2 = [row for row in reader]  # 空

"""
因为还没有关闭文件,先要移动文件光标,再新建迭代器才有效
"""
    fp.seek(0)

    reader2 = csv.reader(fp)
    row3 = [row for row in reader2] # 正常读入

2.读一列

import csv
with open("test.csv") as f:
    reader = csv.reader(f)
    column = [row[1] for row in reader]  # 第1列
    print(column)

3.写

import csv
with open("test.csv", "a") as f:
    row1 = ['曹操', '23', '学生', '黑龙江', '5000']
    writer = csv.writer(f)
    writer.writerow(row1)

 4.列最大值

"""
获取某列最大值
"""
import csv
with open("test.csv", "r") as f:
    reader = csv.reader(f)
    head_row = next(reader)                         # 先排除掉表头
    column = [row[4] for row in reader if row!=[]]  # 末尾有空行,靠if排除
    print(column)                                   # list中每个元素都是字符串
    print(max(column, key=lambda x: eval(x)))       # 要计算需要转成int类型

 5.复制csv文件

import csv
with open("test1.csv", "w", newline='') as fp:
    """
    注意消除空行：newline='',不然写入时每行后都会增加一个空行
    """
    with open("test.csv", "r") as fp1:
        reader = csv.reader(fp1)
        data = [row for row in reader]
        writer = csv.writer(fp)
        for row in data:
            writer.writerow(row)

四、json <-> csv 

1.csv->json

import csv
import json
"""
1.读csv中的所有行,每行每列与表头组合，转换为字典
"""
with open("test.csv", "r") as fp1:
    reader = csv.reader(fp1)
    data = [row for row in reader]
    print(data)
    keys = data[0]
    values = data[1:]
    res = [dict(zip(keys, value)) for value in values]
    print(res)
"""
2.将处理好的数据,写进json文件
"""
with open("test.json", "w") as fp:
    json.dump(res, fp, indent=4, separators=(',', ':'))

2.json->csv

import json
import csv
with open("test.json", "r") as fp1:
    data = json.load(fp1)
    keys = [key for key, value in data[0].items()]  # 表头
    values = [list(item.values()) for item in data] # 后面每一行
    print(keys)
    print(values)
    res = [keys] + values
"""
注意前一个要再套一个[],不然values会直接嵌在keys后面
"""

with open("test.csv", "w", newline="") as fp:
    writer = csv.writer(fp)
    for row in res:
        writer.writerow(row)

五、excel文件操作

import openpyxl
# 1：打开工作簿
wb = openpyxl.load_workbook("超市营业额1.xlsx")
# 2：选取表单
sh = wb['Sheet1']
# 3：读表头
head_row = list(sh.rows)[0]
print(head_row)
# 4：读后续行
for row in list(sh.rows)[1:]:
    case_id = row[0].value
    case_name = row[1].value
    case_date = row[2].value

wb.close()

六、编码方式