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1 ========================== |
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2 Outputting CSV with Django |
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3 ========================== |
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4 |
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5 This document explains how to output CSV (Comma Separated Values) dynamically |
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6 using Django views. To do this, you can either use the `Python CSV library`_ or |
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7 the Django template system. |
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8 |
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9 .. _Python CSV library: http://docs.python.org/library/csv.html |
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10 |
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11 Using the Python CSV library |
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12 ============================ |
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13 |
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14 Python comes with a CSV library, ``csv``. The key to using it with Django is |
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15 that the ``csv`` module's CSV-creation capability acts on file-like objects, and |
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16 Django's :class:`~django.http.HttpResponse` objects are file-like objects. |
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17 |
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18 Here's an example:: |
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19 |
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20 import csv |
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21 from django.http import HttpResponse |
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22 |
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23 def some_view(request): |
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24 # Create the HttpResponse object with the appropriate CSV header. |
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25 response = HttpResponse(mimetype='text/csv') |
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26 response['Content-Disposition'] = 'attachment; filename=somefilename.csv' |
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27 |
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28 writer = csv.writer(response) |
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29 writer.writerow(['First row', 'Foo', 'Bar', 'Baz']) |
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30 writer.writerow(['Second row', 'A', 'B', 'C', '"Testing"', "Here's a quote"]) |
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31 |
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32 return response |
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33 |
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34 The code and comments should be self-explanatory, but a few things deserve a |
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35 mention: |
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36 |
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37 * The response gets a special MIME type, ``text/csv``. This tells |
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38 browsers that the document is a CSV file, rather than an HTML file. If |
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39 you leave this off, browsers will probably interpret the output as HTML, |
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40 which will result in ugly, scary gobbledygook in the browser window. |
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41 |
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42 * The response gets an additional ``Content-Disposition`` header, which |
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43 contains the name of the CSV file. This filename is arbitrary; call it |
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44 whatever you want. It'll be used by browsers in the "Save as..." |
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45 dialogue, etc. |
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46 |
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47 * Hooking into the CSV-generation API is easy: Just pass ``response`` as the |
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48 first argument to ``csv.writer``. The ``csv.writer`` function expects a |
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49 file-like object, and :class:`~django.http.HttpResponse` objects fit the |
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50 bill. |
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51 |
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52 * For each row in your CSV file, call ``writer.writerow``, passing it an |
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53 iterable object such as a list or tuple. |
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54 |
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55 * The CSV module takes care of quoting for you, so you don't have to worry |
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56 about escaping strings with quotes or commas in them. Just pass |
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57 ``writerow()`` your raw strings, and it'll do the right thing. |
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58 |
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59 Handling Unicode |
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60 ~~~~~~~~~~~~~~~~ |
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61 |
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62 Python's ``csv`` module does not support Unicode input. Since Django uses |
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63 Unicode internally this means strings read from sources such as |
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64 :class:`~django.http.HttpRequest` are potentially problematic. There are a few |
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65 options for handling this: |
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66 |
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67 * Manually encode all Unicode objects to a compatible encoding. |
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68 |
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69 * Use the ``UnicodeWriter`` class provided in the `csv module's examples |
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70 section`_. |
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71 |
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72 * Use the `python-unicodecsv module`_, which aims to be a drop-in |
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73 replacement for ``csv`` that gracefully handles Unicode. |
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74 |
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75 For more information, see the Python `CSV File Reading and Writing`_ |
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76 documentation. |
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77 |
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78 .. _`csv module's examples section`: http://docs.python.org/library/csv.html#examples |
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79 .. _`python-unicodecsv module`: https://github.com/jdunck/python-unicodecsv |
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80 .. _`CSV File Reading and Writing`: http://docs.python.org/library/csv.html |
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81 |
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82 Using the template system |
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83 ========================= |
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84 |
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85 Alternatively, you can use the :doc:`Django template system </topics/templates>` |
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86 to generate CSV. This is lower-level than using the convenient Python ``csv`` |
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87 module, but the solution is presented here for completeness. |
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88 |
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89 The idea here is to pass a list of items to your template, and have the |
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90 template output the commas in a :ttag:`for` loop. |
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91 |
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92 Here's an example, which generates the same CSV file as above:: |
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93 |
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94 from django.http import HttpResponse |
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95 from django.template import loader, Context |
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96 |
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97 def some_view(request): |
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98 # Create the HttpResponse object with the appropriate CSV header. |
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99 response = HttpResponse(mimetype='text/csv') |
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100 response['Content-Disposition'] = 'attachment; filename=somefilename.csv' |
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101 |
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102 # The data is hard-coded here, but you could load it from a database or |
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103 # some other source. |
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104 csv_data = ( |
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105 ('First row', 'Foo', 'Bar', 'Baz'), |
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106 ('Second row', 'A', 'B', 'C', '"Testing"', "Here's a quote"), |
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107 ) |
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108 |
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109 t = loader.get_template('my_template_name.txt') |
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110 c = Context({ |
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111 'data': csv_data, |
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112 }) |
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113 response.write(t.render(c)) |
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114 return response |
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115 |
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116 The only difference between this example and the previous example is that this |
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117 one uses template loading instead of the CSV module. The rest of the code -- |
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118 such as the ``mimetype='text/csv'`` -- is the same. |
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119 |
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120 Then, create the template ``my_template_name.txt``, with this template code: |
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121 |
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122 .. code-block:: html+django |
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123 |
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124 {% for row in data %}"{{ row.0|addslashes }}", "{{ row.1|addslashes }}", "{{ row.2|addslashes }}", "{{ row.3|addslashes }}", "{{ row.4|addslashes }}" |
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125 {% endfor %} |
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126 |
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127 This template is quite basic. It just iterates over the given data and displays |
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128 a line of CSV for each row. It uses the :tfilter:`addslashes` template filter to |
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129 ensure there aren't any problems with quotes. |
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130 |
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131 Other text-based formats |
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132 ======================== |
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133 |
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134 Notice that there isn't very much specific to CSV here -- just the specific |
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135 output format. You can use either of these techniques to output any text-based |
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136 format you can dream of. You can also use a similar technique to generate |
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137 arbitrary binary data; see :doc:`/howto/outputting-pdf` for an example. |