Re: What I learned today

2020-02-15 Thread Peter Otten 
Stefan Ram wrote:

> The other thing I read in a book. I already knew that one
> can zip using ... »zip«. E.g.,
> 
> x =( 'y', 'n', 'a', 'n', 't' )
> y =(   4,   2,   7,  3,1 )
> z = zip( x, y )
> print( list( z ))
> [('y', 4), ('n', 2), ('a', 7), ('n', 3), ('t', 1)]
> 
> But the book told me that you can unzip using ... »zip« again!
> 
> z = zip( x, y )
> a, b = zip( *z )
> print( a )
> ('y', 'n', 'a', 'n', 't')
> print( b )
> (4, 2, 7, 3, 1)
> 
> Wow!
> 

Another way to look at that is that if you write a matrix as a tuple of 
tuples

>>> a = (1,2), (3,4), (5,6)

you can transpose it with

>>> def transposed(a):
... return tuple(zip(*a))
... 
>>> transposed(a)
((1, 3, 5), (2, 4, 6))

and transposing twice gives the original matrix:

>>> transposed(transposed(a)) == a
True


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I can't access dataframe fields

2020-02-15 Thread Markos 

Hi all,

I created the following data frame (updated_distance_matrix)

 P1    P2    P4    P5   (P3, P6)
P1 0,00 0,244307 0,367696 0,341760 0
P2 0.234307 0.00 0.194165 0.1443178 0
P4 0.366969 0.194165 0.00 0.284253 0
P5 0.341760 0.1443178 0.284253 0.00 0
(P3, P6) 0.00 0.00 0.00 0.00 0

I can change the fields of columns and rows P1-P5 without problems.

But when I try to access the fields of the row, or column, (P3, P6)

print (updated_distance_matrix_df.loc [clusters [i], last_cluster])

the message appears:

KeyError: 'the label [P3, P6] is not in the [index]'

If I change find the "loc" by "at" method appears the error:

print (updated_distance_matrix_df.at [clusters [i], last_cluster])

TypeError: unhashable type: 'list'

And if you simply leave:

print (updated_distance_matrix_df [clusters [i], last_cluster])

gives the error:

TypeError: unhashable type: 'list'

A last_cluster variable is of type list:

print (last_cluster, type (last_cluster))

['P3', 'P6'] 

And a variable cluster [i] is a string:

print (clusters [i], type (clusters [i]))

P5 

Any tip?

Thank you,

Markos

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Re: I can't access dataframe fields

2020-02-15 Thread MRAB 

On 2020-02-16 00:50, Markos wrote:

Hi all,

I created the following data frame (updated_distance_matrix)

   P1    P2    P4    P5   (P3, P6)
P1 0,00 0,244307 0,367696 0,341760 0
P2 0.234307 0.00 0.194165 0.1443178 0
P4 0.366969 0.194165 0.00 0.284253 0
P5 0.341760 0.1443178 0.284253 0.00 0
(P3, P6) 0.00 0.00 0.00 0.00 0

I can change the fields of columns and rows P1-P5 without problems.

But when I try to access the fields of the row, or column, (P3, P6)

print (updated_distance_matrix_df.loc [clusters [i], last_cluster])

the message appears:

KeyError: 'the label [P3, P6] is not in the [index]'

The rows and columns have "(P3, P6)", but you're looking for "[P3, P6]". 
They aren't the same.



If I change find the "loc" by "at" method appears the error:

print (updated_distance_matrix_df.at [clusters [i], last_cluster])

TypeError: unhashable type: 'list'

Is it expecting a tuple instead of a list? Tuples are hashable, lists 
are not.



And if you simply leave:

print (updated_distance_matrix_df [clusters [i], last_cluster])

gives the error:

TypeError: unhashable type: 'list'

A last_cluster variable is of type list:

print (last_cluster, type (last_cluster))

['P3', 'P6'] 

And a variable cluster [i] is a string:

print (clusters [i], type (clusters [i]))

P5 

Any tip?

Thank you,


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