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1 | .. _autoawait: | ||
2 | .. autoawait: |
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4 | Asynchronous in REPL: Autoawait |
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3 | Asynchronous in REPL: Autoawait | |
5 | =============================== |
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4 | =============================== | |
6 |
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5 | |||
7 | Starting with IPython 6.0, and when user Python 3.6 and above, IPython offer the |
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6 | Starting with IPython 6.0, and when user Python 3.6 and above, IPython offer the | |
8 | ability to run asynchronous code from the REPL. constructs which are |
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7 | ability to run asynchronous code from the REPL. constructs which are | |
9 | :exc:`SyntaxError` s in the Python REPL can be used seamlessly in IPython. |
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8 | :exc:`SyntaxError` s in the Python REPL can be used seamlessly in IPython. | |
10 |
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9 | |||
11 | When a supported libray is used, IPython will automatically `await` Futures |
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10 | When a supported libray is used, IPython will automatically `await` Futures | |
12 | and Coroutines in the REPL. This will happen if an :ref:`await <await>` (or `async`) is |
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11 | and Coroutines in the REPL. This will happen if an :ref:`await <await>` (or `async`) is | |
13 | use at top level scope, or if any structure valid only in `async def |
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12 | use at top level scope, or if any structure valid only in `async def | |
14 | <https://docs.python.org/3/reference/compound_stmts.html#async-def>`_ function |
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13 | <https://docs.python.org/3/reference/compound_stmts.html#async-def>`_ function | |
15 | context are present. For example, the following being a syntax error in the |
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14 | context are present. For example, the following being a syntax error in the | |
16 | Python REPL:: |
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15 | Python REPL:: | |
17 |
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16 | |||
18 | Python 3.6.0 |
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17 | Python 3.6.0 | |
19 | [GCC 4.2.1] |
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18 | [GCC 4.2.1] | |
20 | Type "help", "copyright", "credits" or "license" for more information. |
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19 | Type "help", "copyright", "credits" or "license" for more information. | |
21 | >>> import aiohttp |
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20 | >>> import aiohttp | |
22 | >>> result = aiohttp.get('https://api.github.com') |
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21 | >>> result = aiohttp.get('https://api.github.com') | |
23 | >>> response = await result |
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22 | >>> response = await result | |
24 | File "<stdin>", line 1 |
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23 | File "<stdin>", line 1 | |
25 | response = await result |
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24 | response = await result | |
26 | ^ |
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25 | ^ | |
27 | SyntaxError: invalid syntax |
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26 | SyntaxError: invalid syntax | |
28 |
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27 | |||
29 | Should behave as expected in the IPython REPL:: |
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28 | Should behave as expected in the IPython REPL:: | |
30 |
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29 | |||
31 | Python 3.6.0 |
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30 | Python 3.6.0 | |
32 | Type 'copyright', 'credits' or 'license' for more information |
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31 | Type 'copyright', 'credits' or 'license' for more information | |
33 | IPython 6.0.0.dev -- An enhanced Interactive Python. Type '?' for help. |
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32 | IPython 6.0.0.dev -- An enhanced Interactive Python. Type '?' for help. | |
34 |
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33 | |||
35 | In [1]: import aiohttp |
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34 | In [1]: import aiohttp | |
36 | ...: result = aiohttp.get('https://api.github.com') |
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35 | ...: result = aiohttp.get('https://api.github.com') | |
37 |
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36 | |||
38 | In [2]: response = await result |
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37 | In [2]: response = await result | |
39 | <pause for a few 100s ms> |
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38 | <pause for a few 100s ms> | |
40 |
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39 | |||
41 | In [3]: await response.json() |
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40 | In [3]: await response.json() | |
42 | Out[3]: |
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41 | Out[3]: | |
43 | {'authorizations_url': 'https://api.github.com/authorizations', |
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42 | {'authorizations_url': 'https://api.github.com/authorizations', | |
44 | 'code_search_url': 'https://api.github.com/search/code?q={query}...', |
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43 | 'code_search_url': 'https://api.github.com/search/code?q={query}...', | |
45 | ... |
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44 | ... | |
46 | } |
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45 | } | |
47 |
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46 | |||
48 |
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47 | |||
49 | You can use the ``c.InteractiveShell.autoawait`` configuration option and set it |
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48 | You can use the ``c.InteractiveShell.autoawait`` configuration option and set it | |
50 | to :any:`False` to deactivate automatic wrapping of asynchronous code. You can also |
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49 | to :any:`False` to deactivate automatic wrapping of asynchronous code. You can also | |
51 | use the :magic:`%autoawait` magic to toggle the behavior at runtime:: |
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50 | use the :magic:`%autoawait` magic to toggle the behavior at runtime:: | |
52 |
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51 | |||
53 | In [1]: %autoawait False |
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52 | In [1]: %autoawait False | |
54 |
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53 | |||
55 | In [2]: %autoawait |
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54 | In [2]: %autoawait | |
56 | IPython autoawait is `Off`, and set to use `IPython.core.interactiveshell._asyncio_runner` |
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55 | IPython autoawait is `Off`, and set to use `IPython.core.interactiveshell._asyncio_runner` | |
57 |
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56 | |||
58 |
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57 | |||
59 |
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58 | |||
60 | By default IPython will assume integration with Python's provided |
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59 | By default IPython will assume integration with Python's provided | |
61 | :mod:`asyncio`, but integration with other libraries is provided. In particular |
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60 | :mod:`asyncio`, but integration with other libraries is provided. In particular | |
62 | we provide experimental integration with the ``curio`` and ``trio`` library. |
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61 | we provide experimental integration with the ``curio`` and ``trio`` library. | |
63 |
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62 | |||
64 | You can switch current integration by using the |
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63 | You can switch current integration by using the | |
65 | ``c.InteractiveShell.loop_runner`` option or the ``autoawait <name |
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64 | ``c.InteractiveShell.loop_runner`` option or the ``autoawait <name | |
66 | integration>`` magic. |
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65 | integration>`` magic. | |
67 |
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66 | |||
68 | For example:: |
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67 | For example:: | |
69 |
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68 | |||
70 | In [1]: %autoawait trio |
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69 | In [1]: %autoawait trio | |
71 |
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70 | |||
72 | In [2]: import trio |
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71 | In [2]: import trio | |
73 |
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72 | |||
74 | In [3]: async def child(i): |
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73 | In [3]: async def child(i): | |
75 | ...: print(" child %s goes to sleep"%i) |
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74 | ...: print(" child %s goes to sleep"%i) | |
76 | ...: await trio.sleep(2) |
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75 | ...: await trio.sleep(2) | |
77 | ...: print(" child %s wakes up"%i) |
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76 | ...: print(" child %s wakes up"%i) | |
78 |
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77 | |||
79 | In [4]: print('parent start') |
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78 | In [4]: print('parent start') | |
80 | ...: async with trio.open_nursery() as n: |
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79 | ...: async with trio.open_nursery() as n: | |
81 | ...: for i in range(5): |
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80 | ...: for i in range(5): | |
82 | ...: n.spawn(child, i) |
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81 | ...: n.spawn(child, i) | |
83 | ...: print('parent end') |
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82 | ...: print('parent end') | |
84 | parent start |
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83 | parent start | |
85 | child 2 goes to sleep |
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84 | child 2 goes to sleep | |
86 | child 0 goes to sleep |
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85 | child 0 goes to sleep | |
87 | child 3 goes to sleep |
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86 | child 3 goes to sleep | |
88 | child 1 goes to sleep |
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87 | child 1 goes to sleep | |
89 | child 4 goes to sleep |
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88 | child 4 goes to sleep | |
90 | <about 2 seconds pause> |
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89 | <about 2 seconds pause> | |
91 | child 2 wakes up |
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90 | child 2 wakes up | |
92 | child 1 wakes up |
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91 | child 1 wakes up | |
93 | child 0 wakes up |
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92 | child 0 wakes up | |
94 | child 3 wakes up |
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93 | child 3 wakes up | |
95 | child 4 wakes up |
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94 | child 4 wakes up | |
96 | parent end |
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95 | parent end | |
97 |
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96 | |||
98 |
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97 | |||
99 | In the above example, ``async with`` at top level scope is a syntax error in |
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98 | In the above example, ``async with`` at top level scope is a syntax error in | |
100 | Python. |
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99 | Python. | |
101 |
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100 | |||
102 | Using this mode can have unexpected consequences if used in interaction with |
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101 | Using this mode can have unexpected consequences if used in interaction with | |
103 | other features of IPython and various registered extensions. In particular if you |
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102 | other features of IPython and various registered extensions. In particular if you | |
104 | are a direct or indirect user of the AST transformers, these may not apply to |
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103 | are a direct or indirect user of the AST transformers, these may not apply to | |
105 | your code. |
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104 | your code. | |
106 |
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105 | |||
107 | The default loop, or runner does not run in the background, so top level |
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106 | The default loop, or runner does not run in the background, so top level | |
108 | asynchronous code must finish for the REPL to allow you to enter more code. As |
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107 | asynchronous code must finish for the REPL to allow you to enter more code. As | |
109 | with usual Python semantic, the awaitables are started only when awaited for the |
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108 | with usual Python semantic, the awaitables are started only when awaited for the | |
110 | first time. That is to say, in first example, no network request is done between |
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109 | first time. That is to say, in first example, no network request is done between | |
111 | ``In[1]`` and ``In[2]``. |
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110 | ``In[1]`` and ``In[2]``. | |
112 |
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111 | |||
113 |
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112 | |||
114 | Internals |
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113 | Internals | |
115 | ========= |
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114 | ========= | |
116 |
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115 | |||
117 | As running asynchronous code is not supported in interactive REPL as of Python |
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116 | As running asynchronous code is not supported in interactive REPL as of Python | |
118 | 3.6 we have to rely to a number of complex workaround to allow this to happen. |
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117 | 3.6 we have to rely to a number of complex workaround to allow this to happen. | |
119 | It is interesting to understand how this works in order to understand potential |
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118 | It is interesting to understand how this works in order to understand potential | |
120 | bugs, or provide a custom runner. |
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119 | bugs, or provide a custom runner. | |
121 |
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120 | |||
122 | Among the many approaches that are at our disposition, we find only one that |
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121 | Among the many approaches that are at our disposition, we find only one that | |
123 | suited out need. Under the hood we :ct the code object from a async-def function |
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122 | suited out need. Under the hood we :ct the code object from a async-def function | |
124 | and run it in global namesapace after modifying the ``__code__`` object.:: |
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123 | and run it in global namesapace after modifying the ``__code__`` object.:: | |
125 |
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124 | |||
126 | async def inner_async(): |
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125 | async def inner_async(): | |
127 | locals().update(**global_namespace) |
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126 | locals().update(**global_namespace) | |
128 | # |
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127 | # | |
129 | # here is user code |
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128 | # here is user code | |
130 | # |
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129 | # | |
131 | return last_user_statement |
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130 | return last_user_statement | |
132 | codeobj = modify(inner_async.__code__) |
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131 | codeobj = modify(inner_async.__code__) | |
133 | coroutine = eval(codeobj, user_ns) |
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132 | coroutine = eval(codeobj, user_ns) | |
134 | display(loop_runner(coroutine)) |
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133 | display(loop_runner(coroutine)) | |
135 |
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134 | |||
136 |
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135 | |||
137 |
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136 | |||
138 | The first thing you'll notice is that unlike classical ``exec``, there is only |
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137 | The first thing you'll notice is that unlike classical ``exec``, there is only | |
139 | one name space. Second, user code runs in a function scope, and not a module |
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138 | one name space. Second, user code runs in a function scope, and not a module | |
140 | scope. |
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139 | scope. | |
141 |
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140 | |||
142 | On top of the above there are significant modification to the AST of |
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141 | On top of the above there are significant modification to the AST of | |
143 | ``function``, and ``loop_runner`` can be arbitrary complex. So there is a |
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142 | ``function``, and ``loop_runner`` can be arbitrary complex. So there is a | |
144 | significant overhead to this kind of code. |
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143 | significant overhead to this kind of code. | |
145 |
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144 | |||
146 | By default the generated coroutine function will be consumed by Asyncio's |
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145 | By default the generated coroutine function will be consumed by Asyncio's | |
147 | ``loop_runner = asyncio.get_evenloop().run_until_complete()`` method. It is |
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146 | ``loop_runner = asyncio.get_evenloop().run_until_complete()`` method. It is | |
148 | though possible to provide your own. |
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147 | though possible to provide your own. | |
149 |
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148 | |||
150 | A loop runner is a *synchronous* function responsible from running a coroutine |
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149 | A loop runner is a *synchronous* function responsible from running a coroutine | |
151 | object. |
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150 | object. | |
152 |
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151 | |||
153 | The runner is responsible from ensuring that ``coroutine`` run to completion, |
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152 | The runner is responsible from ensuring that ``coroutine`` run to completion, | |
154 | and should return the result of executing the coroutine. Let's write a |
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153 | and should return the result of executing the coroutine. Let's write a | |
155 | runner for ``trio`` that print a message when used as an exercise, ``trio`` is |
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154 | runner for ``trio`` that print a message when used as an exercise, ``trio`` is | |
156 | special as it usually prefer to run a function object and make a coroutine by |
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155 | special as it usually prefer to run a function object and make a coroutine by | |
157 | itself, we can get around this limitation by wrapping it in an async-def without |
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156 | itself, we can get around this limitation by wrapping it in an async-def without | |
158 | parameters and passing this value to ``trio``:: |
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157 | parameters and passing this value to ``trio``:: | |
159 |
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158 | |||
160 |
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159 | |||
161 | In [1]: import trio |
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160 | In [1]: import trio | |
162 | ...: from types import CoroutineType |
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161 | ...: from types import CoroutineType | |
163 | ...: |
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162 | ...: | |
164 | ...: def trio_runner(coro:CoroutineType): |
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163 | ...: def trio_runner(coro:CoroutineType): | |
165 | ...: print('running asynchronous code') |
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164 | ...: print('running asynchronous code') | |
166 | ...: async def corowrap(coro): |
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165 | ...: async def corowrap(coro): | |
167 | ...: return await coro |
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166 | ...: return await coro | |
168 | ...: return trio.run(corowrap, coro) |
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167 | ...: return trio.run(corowrap, coro) | |
169 |
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168 | |||
170 | We can set it up by passing it to ``%autoawait``:: |
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169 | We can set it up by passing it to ``%autoawait``:: | |
171 |
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170 | |||
172 | In [2]: %autoawait trio_runner |
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171 | In [2]: %autoawait trio_runner | |
173 |
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172 | |||
174 | In [3]: async def async_hello(name): |
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173 | In [3]: async def async_hello(name): | |
175 | ...: await trio.sleep(1) |
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174 | ...: await trio.sleep(1) | |
176 | ...: print(f'Hello {name} world !') |
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175 | ...: print(f'Hello {name} world !') | |
177 | ...: await trio.sleep(1) |
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176 | ...: await trio.sleep(1) | |
178 |
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177 | |||
179 | In [4]: await async_hello('async') |
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178 | In [4]: await async_hello('async') | |
180 | running asynchronous code |
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179 | running asynchronous code | |
181 | Hello async world ! |
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180 | Hello async world ! | |
182 |
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181 | |||
183 |
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182 | |||
184 | Asynchronous programming in python (and in particular in the REPL) is still a |
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183 | Asynchronous programming in python (and in particular in the REPL) is still a | |
185 | relatively young subject. Feel free to contribute improvements to this codebase |
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184 | relatively young subject. Feel free to contribute improvements to this codebase | |
186 | and give us feedback. |
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185 | and give us feedback. |
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