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Date: Sat, 20 Apr 2013 11:09:42 -0600
Subject: itertools.groupby
From: Jason Friedman <jsf80238@gmail.com>
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I have a file such as:

$ cat my_data
Starting a new group
a
b
c
Starting a new group
1
2
3
4
Starting a new group
X
Y
Z
Starting a new group

I am wanting a list of lists:
['a', 'b', 'c']
['1', '2', '3', '4']
['X', 'Y', 'Z']
[]

I wrote this:
------------------------------------
#!/usr/bin/python3
from itertools import groupby

def get_lines_from_file(file_name):
    with open(file_name) as reader:
        for line in reader.readlines():
            yield(line.strip())

counter = 0
def key_func(x):
    if x.startswith("Starting a new group"):
        global counter
        counter += 1
    return counter

for key, group in groupby(get_lines_from_file("my_data"), key_func):
    print(list(group)[1:])
------------------------------------

I get the output I desire, but I'm wondering if there is a solution without
the global counter.

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<div dir=3D"ltr">I have a file such as:<div><br></div><div><div>$ cat my_da=
ta=C2=A0</div><div>Starting a new group<br></div><div>a</div><div>b</div><d=
iv>c</div><div>Starting a new group</div><div>1</div><div>2</div><div>3</di=
v><div>
4</div><div>Starting a new group</div><div>X</div><div>Y</div><div>Z</div><=
div>Starting a new group</div></div><div><br></div><div style>I am wanting =
a list of lists:</div><div style>[&#39;a&#39;, &#39;b&#39;, &#39;c&#39;]<br=
>
</div><div style>[&#39;1&#39;, &#39;2&#39;, &#39;3&#39;, &#39;4&#39;]</div>=
<div style>[&#39;X&#39;, &#39;Y&#39;, &#39;Z&#39;]</div><div style>[]</div>=
<div style><br></div><div style>I wrote this:</div><div style><div>--------=
----------------------------</div>
<div>#!/usr/bin/python3</div><div>from itertools import groupby</div><div><=
br></div><div>def get_lines_from_file(file_name):</div><div>=C2=A0 =C2=A0 w=
ith open(file_name) as reader:</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 for li=
ne in reader.readlines():</div>
<div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 yield(line.strip())</div><di=
v><br></div><div>counter =3D 0</div><div>def key_func(x):</div><div>=C2=A0 =
=C2=A0 if x.startswith(&quot;Starting a new group&quot;):</div><div>=C2=A0 =
=C2=A0 =C2=A0 =C2=A0 global counter</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 c=
ounter +=3D 1</div>
<div>=C2=A0 =C2=A0 return counter</div><div><br></div><div>for key, group i=
n groupby(get_lines_from_file(&quot;my_data&quot;), key_func):</div><div>=
=C2=A0 =C2=A0 print(list(group)[1:])</div><div>----------------------------=
--------<br></div>
</div><div style><div><br></div><div style>I get the output I desire, but I=
&#39;m wondering if there is a solution without the global counter.</div></=
div><div style><br></div></div>

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