【python技巧】替换文件中的某几行,hp 2133

文件名：【python技巧】替换文件中的某几行,hp 2133 【python技巧】替换文件中的某几行

【python技巧】替换文件中的某几行 1. 背景描述2. 单行修改-操作步骤3. 多行修改-操作步骤

1. 背景描述

最近在写一个后端项目，主要的操作就是根据用户的前端数据，在后端打开项目中的代码文件，修改对应位置的参数，因为在目前的后端项目中经常使用这个操作，所以简单总结一下。

1. 文件路径：./test.c2. 文件内容……case EPA:chan_desc->nb_taps = 7;chan_desc->Td = .410;chan_desc->channel_length = (int) (2*chan_desc->sampling_rate*chan_desc->Td + 1 + 2/(M_PI*M_PI)*log(4*M_PI*chan_desc->sampling_rate*chan_desc->Td));sum_amps = 0;chan_desc->amps = (double *) malloc(chan_desc->nb_taps*sizeof(double));chan_desc->free_flags=chan_desc->free_flags|CHANMODEL_FREE_AMPS ;for (i = 0; i<chan_desc->nb_taps; i++) {chan_desc->amps[i] = pow(10,.1*epa_amps_dB[i]);sum_amps += chan_desc->amps[i];}for (i = 0; i<chan_desc->nb_taps; i++)chan_desc->amps[i] /= sum_amps;chan_desc->delays = epa_delays;chan_desc->ricean_factor = 1;//待修改位置chan_desc->aoa = 0;//待修改位置chan_desc->random_aoa = 0;//待修改位置chan_desc->ch = (struct complexd **) malloc(nb_tx*nb_rx*sizeof(struct complexd *));chan_desc->chF = (struct complexd **) malloc(nb_tx*nb_rx*sizeof(struct complexd *));chan_desc->a = (struct complexd **) malloc(chan_desc->nb_taps*sizeof(struct complexd *));…… 2. 单行修改-操作步骤 读取文件 使用python中的open()函数进行文件读取，将数据存储在缓冲区。 #1. 读取文件path='./test.c'with open(path, 'r') as file:file_content = file.read() 查找文件替换位置 以查找chan_desc->ricean_factor = 1;//待修改位置为例，查找这句话的起点和终点。 ## 注：此步骤需要import re#2. 查找文件替换位置start_index=file_content.find('chan_desc->ricean_factor = ')#起点end_index=file_content.find('chan_desc->aoa = ',start_index)#终点if end_index==-1 or start_index==-1:print('未找到待修改位置')#此时得到的两个指针，分别指向了待修改位置的起点和终点，如下图所示：

设置替换文件内容 假设目前只修改这一行的参数， #3. 设置替换文件内容ricean_factor=3#假设这是要修改的参数信息updata_content=file_content[:start_index]#获取这行代码之前的内容update_content+='chan_desc->ricean_factor = '+str(ricean_factor)+';//待修改位置'#修改这行代码update_content+=file_content[end_index:]#获取这行代码之后的内容#此时得到的update_content就是修改后的完整文件内容，只修改了ricean_factor这一行的值 写入文件 同样使用python中的open函数。 #4. 写入文件if update_content!="":#如果修改内容不为空with open(path, 'w') as file:#w表示覆盖写入，之前的内容都会被覆盖file.write(update_content) 总代码 整体的代码如下所示： import re#1. 读取文件path='./test.c'with open(path, 'r') as file:file_content = file.read()#2. 查找文件替换位置start_index=file_content.find('chan_desc->ricean_factor = ')#起点end_index=file_content.find('chan_desc->aoa = ',start_index)#终点if end_index==-1 or start_index==-1:print('未找到待修改位置')#3. 设置替换文件内容ricean_factor=3#假设这是要修改的参数信息updata_content=file_content[:start_index]#获取这行代码之前的内容update_content+='chan_desc->ricean_factor = '+str(ricean_factor)+';//待修改位置'#修改这行代码update_content+=file_content[end_index:]#获取这行代码之后的内容#4. 写入文件if update_content!="":#如果修改内容不为空with open(path, 'w') as file:#w表示覆盖写入，之前的内容都会被覆盖file.write(update_content) 3. 多行修改-操作步骤 多行修改思路 多行修改有两种修改思路，如果修改部分比较集中，则可直接替换一整块的字符串内容，如果修改部分较为分散，则需要单独查找修改位置，然后再分别进行替换。多行修改-整块替换 try:with open(file_path, "r") as file:file_content = file.read()except Exception as e:return str(e)# 设置改写内容updated_content = ""# 查找修改start_index_1 = file_content.find("start_sentence")#要确保查找元素的唯一性end_index_1 = file_content.find("end_sentence",start_index_1,) if start_index_1 == -1 or end_index_1 == -1:print("未找到待修改位置")return -1# updated_content = file_content[:start_index_1]#获取这行代码之前的内容updated_content += "start_sentence和end_sentence之间的sentence_1;\n"updated_content += "start_sentence和end_sentence之间的sentence_2;\n"updated_content +=file_content[end_index_1:]##此时updated_content就是修改后的完整文件内容if updated_content != "":with open(file_path, "w") as file:file.write(updated_content)else:print("修改失败")return -1 多行修改-局部替换 try:with open(file_path, "r") as file:file_content = file.read()except Exception as e:return str(e)# 设置改写内容updated_content = ""# 查找修改start_index_1 = file_content.find("start_sentence_1")#要确保查找元素的唯一性end_index_1 = file_content.find("end_sentence_1",start_index_1,) start_index_2 = file_content.find("start_sentence_2",end_index_1)end_index_2 = file_content.find("end_sentence_2",start_index_2,)start_index_3 = file_content.find("start_sentence_3",end_index_2)end_index_3 = file_content.find("end_sentence_3",start_index_3,)start_index_4 = file_content.find("start_sentence_4",end_index_3)end_index_4 = file_content.find("end_sentence_4",start_index_4,)if (start_index_1 == -1or end_index_1 == -1or start_index_2 == -1or end_index_2 == -1or start_index_3 == -1or end_index_3 == -1or start_index_4 == -1or end_index_4 == -1):print("未找到待修改位置")return -1# updated_content = file_content[:start_index_1]#获取这行代码之前的内容updated_content += "start_sentence_1和end_sentence_1之间的内容"updated_content +=file_content[end_index_1:start_index_2]updated_content += "start_sentence_2和end_sentence_2之间的内容"updated_content +=file_content[end_index_2:start_index_3]updated_content += "start_sentence_3和end_sentence_3之间的内容"updated_content +=file_content[end_index_3:start_index_4]updated_content += "start_sentence_4和end_sentence_4之间的内容"updated_content += file_content[end_index_4:]##此时updated_content就是修改后的完整文件内容if updated_content != "":with open(file_path, "w") as file:file.write(updated_content)else:print("修改失败")return -1