Ask Your Question
0

Changing a string in a list

asked 2022-03-05 16:26:50 +0200

Cyrille gravatar image

updated 2022-03-05 17:36:25 +0200

I have this huge function which work as expected

def bigM_init(A,signs,b,c,M,cond):
# lines: will be the rows of the matrix
    lines = []
    var=[]
# column: where to put the next nonzero entry
    column = 0
# total number of columns in matrix
    size = len(signs)+signs.count(">=")
    for s in signs:
        if s == '=':
            new = column * [0] + [1] + (size - column - 1) * [0]
            wen=['$a_{}$'.format({column+A.ncols()})]
            column += 1
        elif s == '>=':
            new = column * [0] + [-1, 1] + (size - column - 2) * [0]
            wen=['$\\varepsilon_{}$'.format({column+A.ncols()}),'$a_{}$'.format({column+A.ncols()+1})]
            column += 2
        elif s == '<=':
            new = column * [0] + [1] + (size - column - 1) * [0]
            wen=['$\\varepsilon_{}$'.format({column+A.ncols()})]
            column += 1
        lines.append(new)
        var.append(wen)
    mat = matrix(lines)
    hr=flatten(['$x_{}$'.format({i}) for i in range(0,A.ncols())]+var)
    b1=list(b)
    c1=list(c)
    C0=block_matrix([[A,mat]],subdivide=false)
    C1=list(C0)
    C2=[list(v) for v in C1]
    [C2[i].append(-b1[i]) for i in range(len(C1))]
    H=[v for v in hr if v.startswith('$a_')]
    HH=[hr.index(v) for v in H]
    C3=[flatten([c for c in C2 if c[i]==1]) for i in HH]
    C4=[v[:i] for v,i in zip(C3,HH)]
    C5=[v[i+1:] for v,i in zip(C3,HH)]
    C6=[v+[0]+w for v,w in zip(C4,C5)] 
    C7= [[-M*_ for _ in C6[i]] for i in range(len(C6))]
    C8=matrix(C7)
    C9=list(sum(C8))
    cf= c1+list(zero_vector(SR, len(new)+1))
    C10=[-v+w for v,w in zip(C9,cf)]
    C0p=matrix([list(C0[i])+[b1[i]] for i in range(len(b1))])
    C11m=block_matrix([[C0p],[-matrix(C10)]],subdivide=false)
    C11l=list(block_matrix([[C0p],[-matrix(C10)]],subdivide=false))
    #hc=['']+list(HH)+['$z$']        
    base_init=[]
    for j in range(len(signs)) :
        if signs[j]==">=" :
            base_init.append('$a_{}$'.format({j}))
        if signs[j]=="=" :
            base_init.append('$a_{}$'.format({j}))
        if signs[j]=="<=" :
            base_init.append('$\\varepsilon_{}$'.format({j+len(H)})) 
    hr=list(hr)+list(['$b$'])
    hc=['']+list(base_init)+['$z$'] 
    t = table(C11l, header_row=hr,  header_column=hc,frame=True)
    if cond==0:
        return t
    if cond==1:
        return C11m
    if cond==2:
        return hc
    if cond==3:
        return hr

It can be applied on the following exemple

b=vector([8,6,4])
c=vector([5,4,2])
A=matrix(3,3, [3,2,1,4,3,-1,1,2,2])
signs1 = ['=','>=','<=']
M=100
var=bigM_init(A,signs1,b,c,M,3)
base=bigM_init(A,signs1,b,c,M,2)

show(base)

My first problem is the following, the show(base) output seems weird [,$๐šŠโŽฏ{๐Ÿถ}$,$๐šŠโŽฏ{๐Ÿท}$,$\๐šŸ๐šŠ๐š›๐šŽ๐š™๐šœ๐š’๐š•๐š˜๐š—โŽฏ{๐Ÿบ}$}}$๐šฃ$], (look at the two brakets which must be a coma). But if you ask for show(base[i]) for $i \in {0,..., 4}$ the return is correct. Now I have an other function :

def base_after_pivot(base, veb, vsb):
    #base = base
    #veb = variable entrant dans la base
    #vsb = variable sortant de la base
    hc=[sub.replace(vsb, veb) for sub in base]
    return hc

whose object is to change the name of the elements of the base. In the following context it works

base1=base_after_pivot(base, '$x_0$', '$a_{1}$')
show(base1)

gives the expected output (one more time seeming weird but correct) [,$๐šŠโŽฏ{๐Ÿถ}$,$๐šŠโŽฏ{๐Ÿท}$,$\๐šŸ๐šŠ๐š›๐šŽ๐š™๐šœ๐š’๐š•๐š˜๐š—โŽฏ{๐Ÿบ}$}}$๐šฃ$]. So now I try

base2=base_after_pivot(base, '$x_1$', '$\varepsilon_{4}$')
show(base2)

which doesn't change the base. I hope that some on will find my mistake.

edit retag flag offensive close merge delete

Comments

I would recommend print(base) rather than show, at least if you're using Jupyter and when you're trying to debug. show processes LaTeX and that may hide some things.

John Palmieri gravatar imageJohn Palmieri ( 2022-03-05 19:01:43 +0200 )edit

1 Answer

Sort by ยป oldest newest most voted
1

answered 2022-03-05 17:11:54 +0200

Max Alekseyev gravatar image

updated 2022-03-05 17:12:47 +0200

\ is a special character - you need to double it or use raw strings like:

base2=base_after_pivot(base, '$x_1$', r'$\varepsilon_{4}$')

edit flag offensive delete link more

Comments

Max, I have followed your advice (double it or raw strings) but there is no effect. Sorry, it works when I copied the red command. I suppose there was a non displayed character.

Cyrille gravatar imageCyrille ( 2022-03-05 17:53:48 +0200 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools

1 follower

Stats

Asked: 2022-03-05 16:26:50 +0200

Seen: 136 times

Last updated: Mar 05