Why aren’t all the backslashes being replaced as per replace() statement?

I’m trying to replace backslashes (from this polyline) with double backslashes.

My Script:

txt = "qnkyHbgFYhBi@lFA|@Dz@K~@Oz@An@Dz@A|@D|@M|BJZd@KDHRzBf@lMNrBB~@Lz@h@^`@Lt@?L]`@GH?FJl@Xl@NNLXVpBHV^LZf@Jt@@j@Kx@OjB@l@b@ZJDv@d@`@RXFp@Zl@d@|Ad@`@jAzBf@nATn@xAD~@Jt@TJTv@^b@f@^b@b@f@^r@nA`@^f@`@VVp@Lx@Vb@d@n@l@V|BLx@Hz@Pp@Lz@Fl@ErAFf@K~@IvBQr@m@hBFfAC|@g@nC?z@ANi@hBGjAMx@OvBa@hBWfBSx@?r@M|@Qv@Wn@q@tAMt@@z@Px@kAvDWj@u@pAYr@Mx@q@fA_@d@K~@YTAr@C@@B@`@ITSL}@I]vBz@pA@z@KVGDk@@g@Eg@Kg@@g@Ec@Fe@YSZGFEUUg@Gz@i@j@S|@Wr@Sp@[hBDx@BvBD~@BvCNx@Zj@Z^Zf@TXb@R^Z`@f@FXj@BTOdA]`BUx@Wl@Oz@G|@Hn@At@m@lI@XXf@?v@IBCq@M_AV{BwGLs@To@|@Th@In@`@@cBWmAuAeE[k@e@YYg@a@_@c@YQ[y@aAWa@Us@?iAEk@?{@KaFNy@d@qBh@eDl@s@J@JMLKLT`@R`@X~@b@^^PfAr@Lf@Fd@m@J{ABkALw@d@a@?_AMoA?yCbAqC@s@hBwBXi@Ng@Nu@n@sAMuBJ}@kACs@[e@Wk@e@c@k@YYYIBi@eAMy@A}@Im@G}@JyBDyB?{@IyBC_AKc@_@QgAa@]m@eAo@]e@Om@SsAIy@GwDIwB@}BF}BC]AcEIq@Wq@i@eBMy@AkBUyDIKEvAIZUNK?MFc@ZUGKeAG}@M{DLgAD_ADiFHKtBITm@By@OS[QAUF}@PeBA}AIe@GQc@g@UaBUs@}@gAKi@Ns@A[Kw@GS]g@Ws@I}BOwB?{@SqDA_AQwDAw@g@DEGAu@B}BA}@Fy@Re@Hw@A_AUiAH{@RYXk@EwBG{@OiAAmA"

x = txt.replace("\", "\\")

print(x)

Output (top string has spaces added to highlight the differences to the orginal string below)

qnkyHbgFYhBi@lFA|@Dz@K~@Oz@An@Dz@A|@D|@M|BJZd@KDHRzBf@lMNrBB~@Lz@\h@^`@Lt@?L]`@GH?FJl@Xl@NNLXVpBHV^LZf@Jt@@j@Kx@OjB@l@b@ZJDv@d@`@RXFp@\Zl@d@|Ad@`@jAzBf@nATn@­~    @Jt@TJTv@^b@f@^b@b@f@^r@nA`@^@`    @VVp@Lx@Vb@d@n@\ l@V|BLx@Hz@Pp@Lz@Fl@ErAFf@K~@IvBQr@m@hBFfAC|@g@nC?z@ANi@hBGjAMx@OvBa@hBWfBSx@?r@M|@Qv@Wn@q@tAMt@@z@Px@kAvDWj@u@pAYr@Mx@q@fA_@d@K~@YTAr@C@@B@`@ITSL}@I]vBz@pA@z@KVGDk@@g@Eg@Kg@@g@Ec@Fe@YSZGFEUUg@Gz@i@j@S|@Wr@Sp@[hBDx@BvBD~@BvCNx@Zj@Z^Zf@TXb@R^Z\`@f@FXj@BTOdA]`BUx@Wl@Oz@G|@Hn@At@m@lI@XXf@?v@IBCq@M_AV{B\wGLs@To@|@Th@In@`@@cBWmAuAeE[k@e@YYg@a@_@c@YQ[y@aAWa@Us@?iAEk@?{@KaFNy@d@qBh@eDl@s@J@JMLKLT`@R`@\X~@b@^^PfAr@\Lf@Fd@m@J{ABkALw@d@a@?_AMoA?yCbAqC@s@hBwBXi@Ng@Nu@n@sAMuBJ}@\kACs@[e@Wk@e@c@k@YYYIBi@eAMy@A}@Im@G}@JyBDyB?{@IyBC_AKc@_@QgAa@]m@eAo@]e@Om@SsAIy@GwDIwB@}BF}BC]AcEIq@Wq@i@eBMy@AkBUyDIKEvAIZUNK?MFc@ZUGKeAG}@M{DLgAD_ADiFHKtBITm@By@OS[QAUF}@PeBA}AIe@GQc@g@UaBUs@}@gAKi@Ns@A[Kw@GS]g@Ws@I}BOwB?{@SqDA_AQwDAw@g@DEGAu@B}BA}@Fy@Re@Hw@A_AUiAH{@RYXk@EwBG{@OiAAmA

qnkyHbgFYhBi@lFA|@Dz@K~@Oz@An@Dz@A|@D|@M|BJZd@KDHRzBf@lMNrBB~@Lz@ h@^`@Lt@?L]`@GH?FJl@Xl@NNLXVpBHV^LZf@Jt@@j@Kx@OjB@l@b@ZJDv@d@`@RXFp@ Zl@d@|Ad@`@jAzBf@nATn@ xAD~@Jt@TJTv@^b@f@^b@b@f@^r@nA`@^f@`@VVp@Lx@Vb@d@n@      l@V|BLx@Hz@Pp@Lz@Fl@ErAFf@K~@IvBQr@m@hBFfAC|@g@nC?z@ANi@hBGjAMx@OvBa@hBWfBSx@?r@M|@Qv@Wn@q@tAMt@@z@Px@kAvDWj@u@pAYr@Mx@q@fA_@d@K~@YTAr@C@@B@`@ITSL}@I]vBz@pA@z@KVGDk@@g@Eg@Kg@@g@Ec@Fe@YSZGFEUUg@Gz@i@j@S|@Wr@Sp@[hBDx@BvBD~@BvCNx@Zj@Z^Zf@TXb@R^Z `@f@FXj@BTOdA]`BUx@Wl@Oz@G|@Hn@At@m@lI@XXf@?v@IBCq@M_AV{B wGLs@To@|@Th@In@`@@cBWmAuAeE[k@e@YYg@a@_@c@YQ[y@aAWa@Us@?iAEk@?{@KaFNy@d@qBh@eDl@s@J@JMLKLT`@R`@ X~@b@^^PfAr@ Lf@Fd@m@J{ABkALw@d@a@?_AMoA?yCbAqC@s@hBwBXi@Ng@Nu@n@sAMuBJ}@ kACs@[e@Wk@e@c@k@YYYIBi@eAMy@A}@Im@G}@JyBDyB?{@IyBC_AKc@_@QgAa@]m@eAo@]e@Om@SsAIy@GwDIwB@}BF}BC]AcEIq@Wq@i@eBMy@AkBUyDIKEvAIZUNK?MFc@ZUGKeAG}@M{DLgAD_ADiFHKtBITm@By@OS[QAUF}@PeBA}AIe@GQc@g@UaBUs@}@gAKi@Ns@A[Kw@GS]g@Ws@I}BOwB?{@SqDA_AQwDAw@g@DEGAu@B}BA}@Fy@Re@Hw@A_AUiAH{@RYXk@EwBG{@OiAAmA

So you can see @xAD~@ becomes @­~@ when I would expect it to be @\xAD~@.

Answer

The basic problem is that there are no backslashes in your string. Your source code has backslashes, but they are all escape signals. If you want to retain the backslashes in “WYSIWYG” style, use raw string mode:

txt = r"qnkyHbgFYhB..."

This will retain the characters as seen, without processing the usual escape sequences.