关于Python文件读写

Python中文件操作可以通过open函数，这的确很像C语言中的fopen。通过open函数获取一个file object，然后调用read()，write()等方法对文件进行读写操作。

1.open

使用open打开文件后一定要记得调用文件对象的close()方法。比如可以用try/finally语句来确保最后能关闭文件。

file_object = open('thefile.txt')
try:
    all_the_text = file_object.read( )
finally:
    file_object.close( )

注：不能把open语句放在try块里，因为当打开文件出现异常时，文件对象file_object无法执行close()方法

2.读文件

读文本文件

input = open('data', 'r')
#第二个参数默认为r
input = open('data')

读二进制文件

input = open('data', 'rb')

读取所有内容

file_object = open('thefile.txt')
try:
    all_the_text = file_object.read( )
finally:
    file_object.close( )

读固定字节

file_object = open('abinfile', 'rb')
try:
    while True:
        chunk = file_object.read(100)
        if not chunk:
            break
        do_something_with(chunk)
finally:
    file_object.close( )

如果文件是文本文件，还可以直接遍历文件对象获取每行：

for line in file_object:
    process line

3.写文件

写文本文件

output = open('data', 'w')

写二进制文件

output = open('data', 'wb')

写数据

file_object = open('thefile.txt', 'w')
file_object.write(all_the_text)
file_object.close( )

成绩表修改

# -*- coding:utf-8

import pandas as pd

def ExcelToCsv_1(StartName, SheetName, EndName):

    grade = pd.read_excel(StartName, sheet_name=SheetName)
    for i in range(len(grade.index)):
        for j in range(1, len(grade.columns)):
            if grade.iloc[i, j] == '优秀':
                grade.iat[i, j] = 90
            elif grade.iloc[i, j] == '良好':
                grade.iat[i, j] = 80
            elif grade.iloc[i, j] == '合格':
                grade.iat[i, j] = 60
            else:
                grade.iat[i, j] = 0
    grade.to_csv(EndName)

def ExcelToCsv_2(StartName, SheetName, EndName):
    grade = pd.read_excel(StartName, sheet_name=SheetName)
    Grade = grade.replace("优秀", "")
    Grade = Grade.replace("良好", "")
    Grade = Grade.replace("不合格", "")
    Grade = Grade.replace("合格", "")
    Grade = Grade.fillna(value = 0)
    Grade.to_csv(EndName)

ExcelToCsv_2("D:\\Python成绩(1)", "Sheet1", "D:\\Python成绩(1).csv")
ExcelToCsv_1("D:\\Python成绩登记信计(1)", "Sheet1", "D:\\Python成绩登记信计(1).csv")

如图：

使用第三方库pandas将xlsx文件转csv文件

import pandas as pd

def xlsx_to_csv_pd():
    data_xls = pd.read_excel('1.xlsx', index_col=0)
    data_xls.to_csv('1.csv', encoding='utf-8')

if __name__ == '__main__':
    xlsx_to_csv_pd()