Thank you so much sir for your advice.

On Fri, Aug 31, 2018 at 8:48 PM Anton Akhmerov <anton.akhmerov+kd@gmail.com> wrote:
Dear Shyam Lochan Bora,

Right now your question is rather poorly formulated, and not suitable
for this mailing list. Please read this instruction on how to ask good
questions: https://stackoverflow.com/help/how-to-ask
Additionally, it appears that your problem is due the lack of the
Python knowledge, I recommend you to follow a Python course, or
otherwise learn the language more systematically.

Best regards,
Anton Akhmerov
On Fri, Aug 31, 2018 at 5:08 PM shyam lochan bora
<shyamlochan04@gmail.com> wrote:
>
> Dear sir,
> Please help me with the following error in the program
> from __future__ import print_function
> from ipywidgets import interact, interactive, fixed, interact_manual
> import ipywidgets as widgets
> import kwant
> from matplotlib import pyplot
> import numpy as np
> from holoviews.core.options import Cycle
> from types import SimpleNamespace
>
> def nanowire_chain():
>     lat = kwant.lattice.chain()
>     sys = kwant.Builder(kwant.TranslationalSymmetry(*lat.prim_vecs))
>
>     def onsite(onsite, p):
>         return (2 * p.t - p.mu) * pauli.szs0 + p.B * (np.cos(p.phi)*pauli.s0sz+ np.sin(p.phi)*np.sin(p.theta)*pauli.s0sy+np.sin(p.phi)*np.sin(p.theta)*pauli.s0sx)+ p.delta * pauli.sxs0
>
>     sys[lat(0)] = onsite
>
>     def hop(site1, site2, p):
>         return -p.t * pauli.szs0 - .5j * p.alpha * pauli.szsx
>
>     sys[kwant.HoppingKind((1,), lat)] = hop
>
>     return sys
>
>
> def spinful_kitaev_chain():
>     lat = kwant.lattice.chain()
>     sys = kwant.Builder(kwant.TranslationalSymmetry(*lat.prim_vecs))
>
>     def onsite(site, p):
>         return (2 * p.t - p.mu) * pauli.szs0 + p.B * pauli.szsz
>
>     sys[lat(0)] = onsite
>
>     def hop(site1, site2, p):
>         return -p.t * pauli.szs0 - 1j * p.delta * pauli.sys0
>
>     sys[kwant.HoppingKind((1,), lat)] = hop
>
>     return sys
>
>
> def find_gap(sys, p, resolution=1e-4):
>     """Find gap in a system by doing a binary search in energy."""
>
>     # This tells us if there are modes at a certain energy.
>     if len(sys.modes(energy=0, args=[p])[0].momenta):
>         return 0
>
>     gap = step = min(abs(kwant.physics.Bands(sys, args=[p])(k=0))) / 2
>     while step > resolution:
>         step /= 2
>         if len(sys.modes(gap, args=[p])[0].momenta):
>             gap -= step
>         else:
>             gap += step
>
>     return gap
>
>
> def spinorbit_band_gap(sys, mu, t, delta, Bs):
>     sys = sys.finalized()
>     alphas = [0.0, 0.1, 0.2, 0.3]
>     p = SimpleNamespace(mu=mu, t=t, delta=delta,theta=theta,phi=phi)
>
>     def gap(sys, p, alpha, B):
>         p.alpha = alpha
>         p.B = B
>         return find_gap(sys, p)
>
>     gaps = [gap(sys, p, alpha, B) for alpha in alphas for B in Bs]
>     gaps = np.reshape(gaps, (len(alphas), -1))
>     dims = {'kdims': [r'$B$'], 'vdims': ['Band gap']}
>     B_crit = holoviews.VLine(np.sqrt(p.delta**2 + p.mu**2))
>     plot = [holoviews.Curve((Bs, gaps[i]), label=r'$\alpha={}$'.format(
>         alphas[i]), **dims) * B_crit for i, alpha in enumerate(alphas)]
>     title = r'$\Delta={delta}$, $\mu={mu}$'.format(delta=np.round(p.delta, 2), mu=np.round(p.mu, 2))
>     style = {'xticks': [0, 0.1, 0.2, 0.3], 'yticks': [0, 0.05, 0.1], 'fig_size': 150}
>     plot = holoviews.Overlay(plot)
>     return plot(plot=style)
>
>
> def title(p):
>     try:
>         title = r"$\alpha={alpha}$, $\mu={mu}$, $B={B}$, $\Delta={delta}$"
>         title = title.format(alpha=np.round(p.alpha, 2),
>                              mu=np.round(p.mu, 2),
>                              B=np.round(p.B, 2),
>                              delta=np.round(p.delta, 2))
>     except AttributeError:
>         title = r"$\mu={mu}$, $B={B}$, $\Delta={delta}$"
>         title = title.format(mu=np.round(p.mu, 2),
>                              B=np.round(p.B, 2),
>                              delta=np.round(p.delta, 2))
>     return title
>
> style = {'k_x': np.linspace(-1, 1, 101),
>          'xdim': r'$k$',
>          'ydim': r'$E/t$',
>          'xticks': [-1, 0, 1],
>          'yticks': [-1, 0, 1],
>          'xlims': [-1, 1],
>          'ylims': [-1.5, 1.5],
>          'title': title}
> sys = nanowire_chain()
> p = SimpleNamespace(t=1, mu=0.1, delta=0.1, B=0.3,theta=np.pi/2,phi=np.pi/2)
> alphas = np.linspace(0, 0.4, 10)
> holoviews.HoloMap({alpha: spectrum(sys, p.update(alpha=alpha), **style) for alpha in alphas}, kdims=[r'$\alpha$'])
>
> c:\python36\lib\site-packages\kwant\linalg\lll.py:103: FutureWarning: rcond parameter will change to the default of machine precision times max(M, N) where M and N are the input matrix dimensions.
> To use the future default and silence this warning we advise to pass rcond=None, to keep using the old, explicitly pass rcond=-1.
>   coefs = np.linalg.lstsq(vecs_orig.T, vecs.T)[0]
> c:\python36\lib\site-packages\kwant\linalg\lll.py:144: FutureWarning: rcond parameter will change to the default of machine precision times max(M, N) where M and N are the input matrix dimensions.
> To use the future default and silence this warning we advise to pass rcond=None, to keep using the old, explicitly pass rcond=-1.
>   center_coords = np.array(np.round(np.linalg.lstsq(basis.T, vec)[0]), int)
>
> ---------------------------------------------------------------------------
> NameError                                 Traceback (most recent call last)
> <ipython-input-3-9ff9219a759e> in <module>()
>       2 p = SimpleNamespace(t=1, mu=0.1, delta=0.1, B=0.3,theta=np.pi/2,phi=np.pi/2)
>       3 alphas = np.linspace(0, 0.4, 10)
> ----> 4 holoviews.HoloMap({alpha: spectrum(sys, p.update(alpha=alpha), **style) for alpha in alphas}, kdims=[r'$\alpha$'])
>
> NameError: name 'holoviews' is not defined