u10-script-numpy Flashcards
Question;Answer
How do you convert a 2D list to a 1D (flattened) NumPy array?;Use np.array(my_2d_list).flatten() or np.array(my_2d_list).reshape(-1). Both methods will flatten the array into a 1D array.
What are different ways to flatten a 2D Python list to 1D?;1. List comprehension: [element for row in my_2d_list for element in row]\n2. Using sum: `sum(my_2d_list
start=[])\n3. Iterative append: [my_1d_list.append(element) for row in my_2d_list for element in row]`
How do you create a NumPy array of ones with a specific shape and dtype?;Use `np.ones(shape=(rows
cols)
How do you create a range of values in NumPy?;Use np.arange(stop) or `np.arange(start
stop). Example: np.arange(11) creates array [0
How do you select a specific row in a NumPy array?;Use array indexing with the row number: arr[row_index]. Example: arr[0] selects the first row.
How do you select a specific column in a NumPy array?;Use array indexing with a colon and column number: `arr[:
column_index]. Example: arr[:
How do you select the last N rows and columns of a NumPy array?;Use negative slicing: `arr[-N:
-N:]. Example: arr[-3:
What does reshape(-1) do in NumPy?;It flattens an array to 1D
automatically calculating the required length. The -1 tells NumPy to calculate the appropriate dimension size.
How do you reshape a NumPy array to a specific 3D shape?;Use `arr.reshape(dim1
dim2
How do you perform element-wise multiplication in NumPy?;Use the * operator or multiply method. Example: `arr[:
2] *= 3` multiplies all elements in column 3 by 3.
How do you create an array of 64-bit integers in NumPy?;Use the dtype parameter with np.int64: `np.arange(11
dtype=np.int64)`
How do you square all values in a NumPy array?;Use the ** operator: squared = values ** 2
How do you filter values in a NumPy array based on a condition?;Use boolean indexing: arr[arr % 3 == 0] gets all values divisible by 3
What is broadcasting in NumPy?;Broadcasting is NumPy’s way of performing operations on arrays of different shapes. It automatically expands arrays to compatible shapes when possible.
How do you add a new axis to a NumPy array?;Three ways:\n1. `arr[np.newaxis
:]\n2. arr[None
How do you generate random numbers from a uniform distribution in NumPy?;Use np.random.default_rng().random(size) * range. Example: rng.random(10) * 4 generates 10 random numbers between 0 and 4.
How do you find the maximum value in a NumPy array?;Use the max() method or np.max(): arr.max() or np.max(arr)
How do you sort a NumPy array?;Two ways:\n1. In-place: arr.sort()\n2. Create new array: np.sort(arr)
What’s the difference between arr.sort() and np.sort(arr)?;arr.sort() modifies the array in-place
while np.sort(arr) returns a new sorted array leaving the original unchanged.
How do you set a random seed in modern NumPy?;Use rng = np.random.default_rng(seed=value) to create a random number generator with a fixed seed.
