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Python | Flatten a 2d numpy array into 1d array
• Difficulty Level : Basic
• Last Updated : 15 Mar, 2019

Given a 2d numpy array, the task is to flatten a 2d numpy array into a 1d array. Below are a few methods to solve the task.

Method #1 : Using np.flatten()

 `# Python code to demonstrate``# flattening a 2d numpy array``# into 1d array`` ` `import` `numpy as np`` ` `ini_array1 ``=` `np.array([[``1``, ``2``, ``3``], [``2``, ``4``, ``5``], [``1``, ``2``, ``3``]])`` ` `# printing initial arrays``print``(``"initial array"``, ``str``(ini_array1))`` ` `# Multiplying arrays``result ``=` `ini_array1.flatten()`` ` `# printing result``print``(``"New resulting array: "``, result)`
Output:
```initial array [[1 2 3]
[2 4 5]
[1 2 3]]
New resulting array:  [1 2 3 2 4 5 1 2 3]
```

Method #2: Using np.ravel()

 `# Python code to demonstrate``# flattening a 2d numpy array``# into 1d array`` ` `import` `numpy as np`` ` `ini_array1 ``=` `np.array([[``1``, ``2``, ``3``], [``2``, ``4``, ``5``], [``1``, ``2``, ``3``]])`` ` `# printing initial arrays``print``(``"initial array"``, ``str``(ini_array1))`` ` `# Multiplying arrays``result ``=` `ini_array1.ravel()`` ` `# printing result``print``(``"New resulting array: "``, result)`
Output:

```initial array [[1 2 3]
[2 4 5]
[1 2 3]]
New resulting array:  [1 2 3 2 4 5 1 2 3]
```

Method #3: Using np.reshape()

 `# Python code to demonstrate``# flattening a 2d numpy array``# into 1d array`` ` `import` `numpy as np`` ` `ini_array1 ``=` `np.array([[``1``, ``2``, ``3``], [``2``, ``4``, ``5``], [``1``, ``2``, ``3``]])`` ` `# printing initial arrays``print``(``"initial array"``, ``str``(ini_array1))`` ` `# Multiplying arrays``result ``=` `ini_array1.reshape([``1``, ``9``])`` ` `# printing result``print``(``"New resulting array: "``, result)`
Output:
```initial array [[1 2 3]
[2 4 5]
[1 2 3]]
New resulting array:  [[1 2 3 2 4 5 1 2 3]]
```

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