用 Python 替换文本文件的一行中的单个字符

Question

我有一个文本文件，其中所有文件当前都具有相同的结束字符 (N)，用于识别系统取得的进展。我想将结束字符更改为“Y”，以防程序因错误或其他中断而结束，以便在重新启动程序时搜索直到一行具有结束字符“N”并从那里开始工作。以下是我的代码以及文本文件中的示例。

更新代码：

def GeoCode():
    f = open("geocodeLongLat.txt", "a")
    with open("CstoGC.txt",'r') as file:
        print("Geocoding...")
        new_lines = []
        for line in file.readlines():
            check = line.split('~')
            print(check)
            if 'N' in check[-1]:
                geolocator = Nominatim()
                dot_number, entry_name, PHY_STREET,PHY_CITY,PHY_STATE,PHY_ZIP = check[0],check[1],check[2],check[3],check[4],check[5] 
                address = PHY_STREET + " " + PHY_CITY + " " + PHY_STATE + " " + PHY_ZIP
                f.write(dot_number + '\n')
                try:
                    location = geolocator.geocode(address)
                    f.write(dot_number + "," + entry_name + "," + str(location.longitude) + "," + str(location.latitude) + "\n")
                except AttributeError:
                    try:
                        address = PHY_CITY + " " + PHY_STATE + " " + PHY_ZIP
                        location = geolocator.geocode(address)
                        f.write(dot_number + "," + entry_name + "," + str(location.longitude) + "," + str(location.latitude) + "\n")
                    except AttributeError:
                        print("Cannot Geocode")
            check[-1] = check[-1].replace('N','Y')
        new_lines.append('~'.join(check))

    with open('CstoGC.txt','r+') as file: # IMPORTANT to open as 'r+' mode as 'w/w+' will truncate your file!
        for line in new_lines:
            file.writelines(line)        

    f.close()

输出：

2967377~DARIN COLE~22112 TWP RD 209~ALVADA~OH~44802~Y
WAY 64 SUITE 100~EADS~TN~38028~N
384767~MILLER FARMS TRANS LLC~1103 COURT ST~BEDFORD~IA~50833~N
986150~R G S TRUCKING LTD~1765 LOMBARDIE DRIVE~QUESNEL~BC~V2J 4A8~N
1012987~DONALD LARRY KIVETT~4509 LANSBURY RD~GREENSBORO~NC~27406-4509~N
735308~ALZEY EXPRESS INC~2244  SOUTH GREEN STREET~HENDERSON~KY~42420~N
870337~RIES FARMS~1613 255TH AVENUE~EARLVILLE~IA~52057~N
148428~P R MASON & SON LLC~HWY 70 EAST~WILLISTON~NC~28589~N
220940~TEXAS MOVING CO INC~908 N BOWSER RD~RICHARDSON~TX~75081-2869~N
854042~ARMANDO ORTEGA~6590 CHERIMOYA AVENUE~FONTANA~CA~92337~N
940587~DIAMOND A TRUCKING INC~192285 E COUNTY ROAD 55~HARMON~OK~73832~N
1032455~INTEGRITY EXPRESS LLC~380 OLMSTEAD AVENUE~DEPEW~NY~14043~N
889931~DUNSON INC~33 CR 3581~FLORA VISTA~NM~87415~N
143608~LARRY A PETERSON & DONNA M PETERSON~W6359 450TH AVE~ELLSWORTH~WI~54011~N
635528~JAMES E WEBB~3926 GREEN ROAD~SPRINGFIELD~TN~37172~N
805496~WAYNE MLADY~22272 135TH ST~CRESCO~IA~52136~N
704996~SAVINA C MUNIZ~814 W LA QUINTA DR~PHARR~TX~78577~N
893169~BINDEWALD MAINTENANCE INC~213 CAMDEN DR~SLIDELL~LA~70459~N
948130~LOGISTICIZE LTD~861 E PERRY ST~PAULDING~OH~45879~N
438760~SMOOTH OPERATORS INC~W8861 CREEK ROAD~DARIEN~WI~53114~N
518872~A B C RELOCATION SERVICES INC~12 BOCKES ROAD~HUDSON~NH~03051~N
576143~E B D ENTERPRISES INC~29 ROY ROCHE DRIVE~WINNIPEG~MB~R3C 2E6~N
968264~BRIAN REDDEMANN~706 WESTGOR STREET~STORDEN~MN~56174-0220~N
721468~QUALITY LOGISTICS INC~645 LEONARD RD~DUNCAN~SC~29334~N

如您所见，我已经通过使用 x 来跟踪我所在的行。我应该使用类似 file.readlines() 的东西吗？

文本文档示例：

570772~CORPORATE BANK TRANSIT OF KENTUCKY INC~3157 HIGHWAY 64 SUITE 100~EADS~TN~38028~N
384767~MILLER FARMS TRANS LLC~1103 COURT ST~BEDFORD~IA~50833~N
986150~R G S TRUCKING LTD~1765 LOMBARDIE DRIVE~QUESNEL~BC~V2J 4A8~N
1012987~DONALD LARRY KIVETT~4509 LANSBURY RD~GREENSBORO~NC~27406-4509~N
735308~ALZEY EXPRESS INC~2244  SOUTH GREEN STREET~HENDERSON~KY~42420~N
870337~RIES FARMS~1613 255TH AVENUE~EARLVILLE~IA~52057~N
148428~P R MASON & SON LLC~HWY 70 EAST~WILLISTON~NC~28589~N
220940~TEXAS MOVING CO INC~908 N BOWSER RD~RICHARDSON~TX~75081-2869~N
854042~ARMANDO ORTEGA~6590 CHERIMOYA AVENUE~FONTANA~CA~92337~N
940587~DIAMOND A TRUCKING INC~192285 E COUNTY ROAD 55~HARMON~OK~73832~N
1032455~INTEGRITY EXPRESS LLC~380 OLMSTEAD AVENUE~DEPEW~NY~14043~N
889931~DUNSON INC~33 CR 3581~FLORA VISTA~NM~87415~N

谢谢！

编辑：感谢@idlehands 更新代码

Answer 1

我会将整个输入文件读入一个列表，然后 .pop() 一次删除一行。如果出现错误，将弹出的项目附加到列表并覆盖输入文件。这样一来，它将始终是最新的，您不需要任何其他逻辑。

Answer 2

有几种方法可以做到这一点。

选项#1

我最初的想法是使用tell() 和seek() 方法返回几个步骤，但它很快表明，当您不在bytes 中打开文件并且绝对不是在for 循环的 readlines()。您可以在此处查看参考线程：

Is it possible to modify lines in a file in-place?
How to solve "OSError: telling position disabled by next() call"

调查导致了这段代码：

with open('file.txt','rb+') as file:
    line = file.readline() # initiate the loop
    while line: # continue while line is not None
        print(line)
        check = line.split(b'~')[-1]
        if check.startswith(b'N'): # carriage return is expected for each line, strip it

            # ... do stuff ... #

            file.seek(-len(check), 1) # place the buffer at the check point
            file.write(check.replace(b'N', b'Y')) # replace "N" with "Y"
        line = file.readline() # read next line

在第一个引用的线程中，提到的其中一个答案可能会导致您出现潜在问题，并且在读取缓冲区时直接修改缓冲区上的字节可能被认为是一个坏主意™。很多专业人士可能会因为我的建议而责骂我。

选项 #2a

（如果文件大小不是特别大）

with open('file.txt','r') as file:
    new_lines = []
    for line in file.readlines():
        check = line.split('~')
        if 'N' in check[-1]:

            # ... do stuff ... #

            check[-1] = check[-1].replace('N','Y')
        new_lines.append('~'.join(check))

with open('file.txt','r+') as file: # IMPORTANT to open as 'r+' mode as 'w/w+' will truncate your file!
    for line in new_lines:
        file.writelines(line)

这种方法首先将所有行加载到内存中，因此您在内存中进行修改，但不理会缓冲区。然后您重新加载文件并写入已更改的行。需要注意的是，从技术上讲，您正在逐行重写整个文件 - 而不仅仅是字符串 N，即使它是唯一更改的内容。

选项 #2b

从技术上讲，您可以从一开始就以r+ 模式打开文件，然后在迭代完成后执行此操作（仍在with 块内但在循环之外）：

# ... new_lines.append('~'.join(check)) #
    file.seek(0)
    for line in new_lines: 
        file.writelines(line)

我不确定这与选项 #1 有何区别，因为您仍在同时读取和修改文件。如果有更精通 IO/缓冲区/内存管理的人想插话。

选项 2a/b 的缺点是，即使您只剩下几行需要从“N”更新为“Y”，您总是最终会存储和重写文件中的行。

结果（适用于所有解决方案）：

570772~CORPORATE BANK TRANSIT OF KENTUCKY INC~3157 HIGHWAY 64 SUITE 100~EADS~TN~38028~Y
384767~MILLER FARMS TRANS LLC~1103 COURT ST~BEDFORD~IA~50833~Y
986150~R G S TRUCKING LTD~1765 LOMBARDIE DRIVE~QUESNEL~BC~V2J 4A8~Y
1012987~DONALD LARRY KIVETT~4509 LANSBURY RD~GREENSBORO~NC~27406-4509~Y
735308~ALZEY EXPRESS INC~2244  SOUTH GREEN STREET~HENDERSON~KY~42420~Y
870337~RIES FARMS~1613 255TH AVENUE~EARLVILLE~IA~52057~Y
148428~P R MASON & SON LLC~HWY 70 EAST~WILLISTON~NC~28589~Y
220940~TEXAS MOVING CO INC~908 N BOWSER RD~RICHARDSON~TX~75081-2869~Y
854042~ARMANDO ORTEGA~6590 CHERIMOYA AVENUE~FONTANA~CA~92337~Y
940587~DIAMOND A TRUCKING INC~192285 E COUNTY ROAD 55~HARMON~OK~73832~Y
1032455~INTEGRITY EXPRESS LLC~380 OLMSTEAD AVENUE~DEPEW~NY~14043~Y
889931~DUNSON INC~33 CR 3581~FLORA VISTA~NM~87415~Y

如果你说，在以220940 开头的行遇到中断，文件将变为：

570772~CORPORATE BANK TRANSIT OF KENTUCKY INC~3157 HIGHWAY 64 SUITE 100~EADS~TN~38028~Y
384767~MILLER FARMS TRANS LLC~1103 COURT ST~BEDFORD~IA~50833~Y
986150~R G S TRUCKING LTD~1765 LOMBARDIE DRIVE~QUESNEL~BC~V2J 4A8~Y
1012987~DONALD LARRY KIVETT~4509 LANSBURY RD~GREENSBORO~NC~27406-4509~Y
735308~ALZEY EXPRESS INC~2244  SOUTH GREEN STREET~HENDERSON~KY~42420~Y
870337~RIES FARMS~1613 255TH AVENUE~EARLVILLE~IA~52057~Y
148428~P R MASON & SON LLC~HWY 70 EAST~WILLISTON~NC~28589~Y
220940~TEXAS MOVING CO INC~908 N BOWSER RD~RICHARDSON~TX~75081-2869~N
854042~ARMANDO ORTEGA~6590 CHERIMOYA AVENUE~FONTANA~CA~92337~N
940587~DIAMOND A TRUCKING INC~192285 E COUNTY ROAD 55~HARMON~OK~73832~N
1032455~INTEGRITY EXPRESS LLC~380 OLMSTEAD AVENUE~DEPEW~NY~14043~N
889931~DUNSON INC~33 CR 3581~FLORA VISTA~NM~87415~N

这些方法各有利弊。试试看哪一个最适合您的用例。