Q:

How do I open geotiff images with gdal in python?

I am trying to run the following code:
from osgeo import gdal
import sys

# this allows GDAL to throw Python Exceptions
src_ds = gdal.Open( "fused.tif" )
src_ds.show()

But I receive the following error:
Traceback (most recent call last):
    File ".../gdalopen1.py", line 5, in module src_ds.show()
AttributeError: 'Dataset' object has no attribute 'show'

Why does this happen?

A:

You have already opened the dataset, as Spacedman answered. GDAL is not a visualization library (at its core).
You can read the data with:

data = src_ds.ReadAsArray()

And then pass it on the your favourite plotting library. 
Alternatively you could simply output to a more common 'picture' format (PNG for example), and use any viewer you like to display the result.

vmin = 0 # minimum value in your data (will be black in the output)
vmax = 1 # minimum value in your data (will be white in the output)
ds = gdal.Translate('fused.png', 'fused.tif', format='PNG', outputType=gdal.GDT_Byte, scaleParams=[[vmin,vmax]])
ds = None

The scaling is necessary to convert your data values to the 8-bit range (0-255) which commonly used for pictures.

A:

The following code opens a raster file and reads a band of the raster into a numpy array.
from osgeo import gdal
ds = gdal.Open('input.tif', gdal.GA_ReadOnly)
rb = ds.GetRasterBand(1)
img_array = rb.ReadAsArray()

A:

You can do by following,
from osgeo import gdal
gdal.UseExceptions()
ds=gdal.Open('Your Geotif image') 
band= ds.getRasterBand(1)

