353 lines
6.0 KiB
Markdown
353 lines
6.0 KiB
Markdown
# 原创
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： 02-Ipython Magic魔术
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# 02-Ipython Magic魔术
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## IPython Magic 魔术
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具体见个人Python图书馆：[https://ds-ebooks.github.io](https://ds-ebooks.github.io)
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### 简介
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两种`magic`命令： <br/> * `Line magics`：`%`，只接受该行的参数 <br/> * `Cell magics`: `%%`，只能用在`cell`首行，`%%`接收的`magic`参数包括整个`cell`，并且每个单元格只能用一个`cell`
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```
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# 列出可用的魔法命令
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%lsmagic
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```
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```
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Available line magics:
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%alias %alias_magic %autocall %automagic %autosave %bookmark %cd %clear %cls %colors %config %connect_info %copy %ddir %debug %dhist %dirs %doctest_mode %echo %ed %edit %env %gui %hist %history %killbgscripts %ldir %less %load %load_ext %loadpy %logoff %logon %logstart %logstate %logstop %ls %lsmagic %macro %magic %matplotlib %mkdir %more %notebook %page %pastebin %pdb %pdef %pdoc %pfile %pinfo %pinfo2 %popd %pprint %precision %profile %prun %psearch %psource %pushd %pwd %pycat %pylab %qtconsole %quickref %recall %rehashx %reload_ext %ren %rep %rerun %reset %reset_selective %rmdir %run %save %sc %set_env %store %sx %system %tb %time %timeit %unalias %unload_ext %who %who_ls %whos %xdel %xmode
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Available cell magics:
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%%! %%HTML %%SVG %%bash %%capture %%cmd %%debug %%file %%html %%javascript %%js %%latex %%perl %%prun %%pypy %%python %%python2 %%python3 %%ruby %%script %%sh %%svg %%sx %%system %%time %%timeit %%writefile
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Automagic is ON, % prefix IS NOT needed for line magics.
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```
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### 简单`Magic`
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```
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%matplotlib inline
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import numpy as np
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import matplotlib.pyplot as plt
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```
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```
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# %timeit计算代码执行时间
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%timeit np.linalg.eigvals(np.random.rand(100,100))
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```
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```
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100 loops, best of 3: 7.31 ms per loop
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```
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#### 计算整个`cell` 代码运行时间
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```
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%%timeit a = np.random.rand(100, 100)
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np.linalg.eigvals(a)
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```
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```
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100 loops, best of 3: 6.98 ms per loop
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```
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#### `%%capture`捕获`cell`输出`stdout/stderr`
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```
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%%capture capt
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from __future__ import print_function
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import sys
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print('Hello stdout')
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print('and stderr', file=sys.stderr)
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```
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```
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capt.stdout,capt.stderr
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```
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```
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('Hello stdout\n', 'and stderr\n')
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```
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```
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capt.show()
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```
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```
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Hello stdout
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and stderr
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```
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#### `%%capture result`有同样的功能
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```
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%%capture result
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print([1,2,3])
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```
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```
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result.stdout
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```
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```
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'[1, 2, 3]\n'
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```
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```
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result.show()
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```
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```
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[1, 2, 3]
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```
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#### `%%scipy cell magic`
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```
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%%script python
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import sys
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print 'hello from Python %s' % sys.version
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```
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```
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hello from Python 2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:42:59) [MSC v.1500 32 bit (Intel)]
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```
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```
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%%script python3
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import sys
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print('hello from Python: %s' % sys.version)
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```
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```
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hello from Python: 3.6.3 (v3.6.3:2c5fed8, Oct 3 2017, 17:26:49) [MSC v.1900 32 bit (Intel)]
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```
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`IPython`还为一些常见的解释器创建别名，例如`bash，ruby，perl`等。 <br/> 这些都等同于`%% script <name>`
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```
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%%bash
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echo "hello from $BASH"
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```
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```
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hello from /usr/bin/bash
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```
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#### `--out` `--err`捕获`cell`魔法的输出
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```
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%%bash
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echo "hi, stdout"
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echo "hello, stderr" >&2
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```
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```
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hi, stdout
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hello, stderr
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```
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```
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%%bash --out output --err error
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echo "hi, stdout"
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echo "hello, stderr" >&2
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```
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```
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print(error)
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print(output)
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```
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```
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hello, stderr
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hi, stdout
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```
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```
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%matplotlib inline
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import pylab as pl
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pl.seed(1)
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data = pl.randn(100)
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pl.plot(data);
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```
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#### 配合 `%config InlineBackend.figure_format="svg"`做图片输出格式的设置
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```
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%config InlineBackend.figure_format="svg"
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%matplotlib inline
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```
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```
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pl.plot(data);
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```
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#### 调试代码的模式 `%xmode Plain`和原来的模式`%xmode Verbose`
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```
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def f1(a,b):
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return a/b
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def f2(x):
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a = x
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b = x-1
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return f1(a,b)
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```
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```
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# 精简模式
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%xmode Plain
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```
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```
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Exception reporting mode: Plain
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```
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```
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f2(1)
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```
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```
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Traceback (most recent call last):
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File "<ipython-input-22-133f42941cdb>", line 1, in <module>
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f2(1)
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File "<ipython-input-20-05ec2e2678a0>", line 6, in f2
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return f1(a,b)
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File "<ipython-input-20-05ec2e2678a0>", line 2, in f1
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return a/b
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ZeroDivisionError: integer division or modulo by zero
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```
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```
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# 原来的模式
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%xmode Verbose
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```
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```
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Exception reporting mode: Verbose
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```
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```
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f2(1)
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```
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```
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ZeroDivisionErrorTraceback (most recent call last)
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<ipython-input-24-133f42941cdb> in <module>()
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----> 1 f2(1)
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global f2 = <function f2 at 0x0C334CB0>
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<ipython-input-20-05ec2e2678a0> in f2(x=1)
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4 a = x
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5 b = x-1
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----> 6 return f1(a,b)
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global f1 = <function f1 at 0x0C334CF0>
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a = 1
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b = 0
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<ipython-input-20-05ec2e2678a0> in f1(a=1, b=0)
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1 def f1(a,b):
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----> 2 return a/b
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a = 1
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b = 0
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3 def f2(x):
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4 a = x
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5 b = x-1
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ZeroDivisionError: integer division or modulo by zero
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```
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#### `%debug`用户调试错误
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使用`%debug`会在报错时进去调试模式,在调试模式中我们可以
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#### `%timeit`和`%time`
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```
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%timeit sum(map(lambda x:x**2,range(100)))
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```
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```
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10000 loops, best of 3: 18.5 µs per loop
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```
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```
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%time sum(map(lambda x:x**2,range(100)))
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```
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```
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Wall time: 0 ns
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328350
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```
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#### `%%prun/%prun`命令调用`profile`模块，对单元中的代码进行宏观上的性能剖析
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```
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%%prun
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def fib(n):
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if n<2:
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return n
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return fib(n-1)+fib(n-2)
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fib(20)
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```
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像这样：
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```
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21893 function calls (3 primitive calls) in 0.009 seconds
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Ordered by: internal time
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ncalls tottime percall cumtime percall filename:lineno(function)
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21891/1 0.009 0.000 0.009 0.009 <string>:2(fib)
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1 0.000 0.000 0.009 0.009 <string>:2(<module>)
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1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
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```
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### 参考资料
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[Jupyter攻略](http://blog.hszofficial.site/TutorialForJupyter/)
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