\documentclass{article}

% Engine-specific settings
% pdftex:
\ifcsname pdfmatch\endcsname
    \usepackage[T1]{fontenc}
    \usepackage[utf8]{inputenc}
\fi
% xetex:
\ifcsname XeTeXinterchartoks\endcsname
    \usepackage{fontspec}
    \defaultfontfeatures{Ligatures=TeX}
\fi
% luatex:
\ifcsname directlua\endcsname
    \usepackage{fontspec}
\fi
% End engine-specific settings

\usepackage{latex2pydata}

\begin{document}

Test.

\pydatasetfilename{\jobname.pydata}

\pydatawritelistopen

\pydatawritedictopen
\pydatawritekeyvalue{key1 backslash \ double backslash \\ double space  quotes " "" """ """"}{backslash \ double backslash \\ double space  quotes " "" """ """"}
\pydatawritekey{key2 backslash \ double backslash \\ double space  quotes " "" """ """"}
\pydatawritevalue{backslash \ double backslash \\ double space  quotes " "" """ """"}
\pydatawritekey{key3 backslash \ double backslash \\ double space  quotes " "" """ """"}
\begin{pydatawritemlvalue}
backslash \ double backslash \\ double space  quotes " "" """ """"
backslash \ double backslash \\ double space  quotes " "" """ """"
\end{pydatawritemlvalue}
\pydatawritedictclose

\pydatawritedictopen
\pydatasetbuffername{testbuffer}
\pydatabufferkeyvalue{bufkey1 backslash \ double backslash \\ double space  quotes " "" """ """"}{backslash \ double backslash \\ double space  quotes " "" """ """"}
\pydatabufferkey{bufkey2 backslash \ double backslash \\ double space  quotes " "" """ """"}
\pydatabuffervalue{backslash \ double backslash \\ double space  quotes " "" """ """"}
\pydatabufferkey{bufkey3 backslash \ double backslash \\ double space  quotes " "" """ """"}
\begin{pydatabuffermlvalue}
backslash \ double backslash \\ double space  quotes " "" """ """"
backslash \ double backslash \\ double space  quotes " "" """ """"
\end{pydatabuffermlvalue}
\pydatawritebuffer
\pydataclearbuffername{testbuffer}
\pydatawritedictclose

\pydatawritelistclose

\pydataclosefilename{\jobname.pydata}

\end{document}
