# 5.4. Array Concatenation¶

## 5.4.1. 1-dimensional Array¶

>>> import numpy as np
>>>
>>>
>>> a = np.array([1, 2, 3])
>>> b = np.array([4, 5, 6])
>>>
>>> np.concatenate(a, b)
Traceback (most recent call last):
TypeError: only integer scalar arrays can be converted to a scalar index
>>>
>>> np.concatenate((a, b))
array([1, 2, 3, 4, 5, 6])

>>> import numpy as np
>>>
>>>
>>> a = np.array([1, 2, 3])
>>> b = np.array([4, 5, 6])
>>> c = np.array([7, 8, 9])
>>>
>>> np.concatenate((a, b, c))
array([1, 2, 3, 4, 5, 6, 7, 8, 9])

>>> import numpy as np
>>>
>>>
>>> a = np.array([1, 2, 3])
>>> b = np.array([2, 3, 4])
>>>
>>> np.concatenate((a, b))
array([1, 2, 3, 2, 3, 4])


## 5.4.2. 2-dimensional Array¶

>>> import numpy as np
>>>
>>>
>>> a = np.array([[1, 2], [3, 4]])
>>> b = np.array([[5, 6], [7, 8]])
>>>
>>> np.concatenate((a, b))
array([[1, 2],
[3, 4],
[5, 6],
[7, 8]])
>>>
>>> np.concatenate((a, b), axis=0)
array([[1, 2],
[3, 4],
[5, 6],
[7, 8]])
>>>
>>> np.concatenate((a, b), axis=1)
array([[1, 2, 5, 6],
[3, 4, 7, 8]])


## 5.4.3. Assignments¶

"""
* Assignment: Numpy Concatenation
* Complexity: easy
* Lines of code: 1 lines
* Time: 3 min

English:
1. Given are one-dimensional: a: np.ndarray, b: np.ndarray
2. Concatenate them as result: np.ndarray
3. Reshape result into two rows and three columns
4. Run doctests - all must succeed

Polish:
1. Dane są jednowymiarowe: a: np.ndarray, b: np.ndarray
2. Połącz je ze sobą jako result: np.ndarray
3. Przekształć result w dwa wiersze na trzy kolumny
4. Uruchom doctesty - wszystkie muszą się powieść

Tests:
>>> import sys; sys.tracebacklimit = 0

>>> assert result is not Ellipsis, \
'Assign result to variable: result'
>>> assert type(result) is np.ndarray, \
'Variable result has invalid type, expected: np.ndarray'

>>> result
array([[1, 2, 3],
[4, 5, 6]])
"""

import numpy as np

a = np.array([1, 2, 3])
b = np.array([4, 5, 6])

# Concatenate a and b and reshape as 2 by 3
# type: np.ndarray
result = ...