IPython As A Shell - Working With History

IPython maintains a history of all the commands you type. It even maintains this across sessions.

You should work through the commands in this Notebook in an ordinary IPython session since this notebook wan't have any history.

Just history will show you your history.

history [range [range] ...] shows the history in the specified range(s). Here's the note on ranges from the history help.

4
- Line 4, current session
4-6
- Lines 4-6, current session
243/1-5
- Lines 1-5, session 243
~2/7
- Line 7, session 2 before current
~8/1-~6/5
- From the first line of 8 sessions ago, to the fifth line of 6 sessions ago.

Multiple ranges can be entered, separated by spaces

history -n will show you the index number of each command.

history -l <number> shows the last <number> commands.

history -g [pattern [pattern] ...] treats the argument pattern(s) as a glob to search back through your complete history. The pattern may contain ? to match one unknown character and * to match any number of unknown characters. Use '%hist -g'to show full saved history (may be very long).

history -u -g [pattern [pattern] ...] is the same as above but the -u shows only unique commands.

The History Variables

There is also a set of variables that allow you to access previous commands. _i is the previous command and _i2 is the one before, all the way up to _i9.

Let's enter some commands and see how it works.



In [1]:

    
2 + 2









    Out[1]:





4



In [2]:

    
"A string" " connected to another string"









    Out[2]:





'A string connected to another string'



In [3]:

    
num = 3 * (4 + 2)



In [4]:

    
num









    Out[4]:





18



In [5]:

    
strng = "A string" " connected to another string"



In [6]:

    
strng









    Out[6]:





'A string connected to another string'



In [7]:

    
lst = ["word", "two words", "short", "long"]



In [8]:

    
lst









    Out[8]:





['word', 'two words', 'short', 'long']



In [9]:

    
lst[2]









    Out[9]:





'short'



In [10]:

    
lst[:-1]









    Out[10]:





['word', 'two words', 'short']



In [11]:

    
lst[1:]









    Out[11]:





['two words', 'short', 'long']



In [12]:

    
long_list = ["a", "c", "b", "d", "e", "dd", "f", "m", "p", "g"]



In [13]:

    
long_list









    Out[13]:





['a', 'c', 'b', 'd', 'e', 'dd', 'f', 'm', 'p', 'g']



In [14]:

    
long_list[4]









    Out[14]:





'e'



In [15]:

    
long_list[3:7]









    Out[15]:





['d', 'e', 'dd', 'f']

Now we have something to work with.



In [16]:

    
history -n









    



   1: 2 + 2
   2: "A string" " connected to another string"
   3: num = 3 * (4 + 2)
   4: num
   5: strng = "A string" " connected to another string"
   6: strng
   7: lst = ["word", "two words", "short", "long"]
   8: lst
   9: lst[2]
  10: lst[:-1]
  11: lst[1:]
  12: long_list = ["a", "c", "b", "d", "e", "dd", "f", "m", "p", "g"]
  13: long_list
  14: long_list[4]
  15: long_list[3:7]
  16: history -n



In [17]:

    
_i2









    Out[17]:





u'"A string" " connected to another string"'



In [18]:

    
_i4









    Out[18]:





u'num'



In [19]:

    
history -l 6









    



long_list
long_list[4]
long_list[3:7]
history -n
_i2
_i4



In [20]:

    
history -l 7 -n









    



  13: long_list
  14: long_list[4]
  15: long_list[3:7]
  16: history -n
  17: _i2
  18: _i4
  19: history -l 6



In [22]:

    
history -g strng









    



65/5: strng = "A string" " connected to another string"
65/6: strng
   5: strng = "A string" " connected to another string"
   6: strng
  21: history -g "strng"
  22: history -g strng

We can also use those previous commands.



In [23]:

    
%rerun 6









    



=== Executing: ===
strng
=== Output: ===






    Out[23]:





'A string connected to another string'



In [24]:

    
%recall 5



In [25]:

    
strng = "A string" " connected to another string" " with more added this timw"

The %recall command brings back the specified line from history and places it on the input line ready for you to edit before you run it. So in this case I added the third string.



In [26]:

    
strng









    Out[26]:





'A string connected to another string with more added this timw'

The macro magic command allows us to take some lines form our history and turn them into a macro to re-execute them at any time.



In [27]:

    
%macro a_macro 7-11









    



Macro `a_macro` created. To execute, type its name (without quotes).
=== Macro contents: ===
lst = ["word", "two words", "short", "long"]
lst
lst[2]
lst[:-1]
lst[1:]



In [28]:

    
a_macro









    Out[28]:





['two words', 'short', 'long']



In [29]:

    
print a_macro









    



lst = ["word", "two words", "short", "long"]
lst
lst[2]
lst[:-1]
lst[1:]

For other uses of your history check out the edit and save magic commands. (Executing the lines below will pop up the help for each.)



In [30]:

    
edit?



In [31]:

    
save?



In [ ]: