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how to get first three characters of an NSString?
...
mystr=[mystr substringToIndex:3];
Be sure your string has atleast 3 ch.. o.e. it will crash the app.
Here are some other links to check NSsting operations...
Link1
Link2
Apple Link
...
count the frequency that a value occurs in a dataframe column
...requency back to the original dataframe use transform to return an aligned index:
In [41]:
df['freq'] = df.groupby('a')['a'].transform('count')
df
Out[41]:
a freq
0 a 2
1 b 3
2 s 2
3 s 2
4 b 3
5 a 2
6 b 3
[7 rows x 2 columns]
...
How to hide one item in an Android Spinner
... than one item I think that you can implement your own adapter and set the index (or array list of indexes) that you want to hide.
public class CustomAdapter extends ArrayAdapter<String> {
private int hidingItemIndex;
public CustomAdapter(Context context, int textViewResourceId, S...
Appending to an empty DataFrame in Pandas?
...re the output if you want it:
>>> df
Empty DataFrame
Columns: []
Index: []
>>> df = df.append(data)
>>> df
A
0 0
1 1
2 2
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What is git actually doing when it says it is “resolving deltas”?
...t will compress all the "loose" files into a packfile to save space and an index file into that packfile will be created. So zlib will compress with its own delta algorithm but Git does use delta-encoding to store prior versions. Since the most common and frequent access is the latest version, tha...
n-grams in python, four, five, six grams?
... izip, islice, tee
s = 'spam and eggs'
N = 3
trigrams = izip(*(islice(seq, index, None) for index, seq in enumerate(tee(s, N))))
list(trigrams)
# [('s', 'p', 'a'), ('p', 'a', 'm'), ('a', 'm', ' '),
# ('m', ' ', 'a'), (' ', 'a', 'n'), ('a', 'n', 'd'),
# ('n', 'd', ' '), ('d', ' ', 'e'), (' ', 'e', 'g...
mongodb: insert if not exists
...
You could always make a unique index, which causes MongoDB to reject a conflicting save. Consider the following done using the mongodb shell:
> db.getCollection("test").insert ({a:1, b:2, c:3})
> db.getCollection("test").find()
{ "_id" : ObjectId("5...
PHPUnit: assert two arrays are equal, but order of elements not important
...if two associative arrays are similar
*
* Both arrays must have the same indexes with identical values
* without respect to key ordering
*
* @param array $a
* @param array $b
* @return bool
*/
function arrays_are_similar($a, $b) {
// if the indexes don't match, return immediately
if (c...
How to remove the first Item from a list?
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Python List
list.pop(index)
>>> l = ['a', 'b', 'c', 'd']
>>> l.pop(0)
'a'
>>> l
['b', 'c', 'd']
>>>
del list[index]
>>> l = ['a', 'b', 'c', 'd']
>>> del l[0]
>>> l
['b', 'c', 'd'...
SQL join: selecting the last records in a one-to-many relationship
...in one SELECT statement. What is the best practice? Any advice on building indexes?
9 Answers
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