Python Miscellaneous

Links: 108 Python Index

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Use of ellipsis operator (...)

• When arguments of the function are of type any.

def func(abc: ...) -> None:
    pass

• Used as pass statement inside functions

def func() -> None:
    ...

Extending an array in python

a = [1, 2, 3]

b = [10] + a
print(b) # [10, 1, 2, 3]

# similar to JS ... operator
c = [10, *a]
print(c) # [10, 1, 2, 3]

e = [*a, 10]
print(e) # [1, 2, 3, 10]

d = [10]
d.extend(a)
print(d) # [10, 1, 2, 3]

Partial Functions

from functools import partial

def adder(a: int, b: int, c: int) -> int:
    return a + b + c

adder_a = partial(adder, c=12, b=3)
adder_a_b = partial(adder, c=5)

print(adder_a(10)) # 25
print(adder_a_b(a=3, b=5)) # 13
print(adder_a_b(a=3, b=5, c=8)) # 16

Formatting fstrings

# formatting using f strings

text = "text"

# left allignment
print(f"{text:<20} How are you?") # without how are you? you wouldn't have noticed the allignment
print(f"{text:>20}")
print(f"{text:^20}") # centre allignment
# here 20 is the total number of spaces including the text (4 characters)

# we can add any symbol we want
print(f"{text:-^20}") # centre allignment
# if you want spaces before and after text just add them in the string
# for eg: text = " text "

• Output:
  • 

is vs ==

• If you want to compare values use ==. Eg: a == b

• If you want to compare instances use is. Eg: a is True

• Sometimes:

  a = 1000
  b = 1000
  
  print(a is b)
  # this might result as True since python assigns them the same id to save space.
  

• Example:

  class A:
      def __init__(self):
          pass
  
  test_a = A()
  test_b = B()
  
  print(test_a == test_b) # False
  print(test_a is test_b) # True
  
  # test_a and test_b are two separate instances but they have the same value
  

References

• THE CRUCIAL DIFFERENCE BETWEEN "is" & "\==" IN PYTHON 2022 - YouTube

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Last updated: 2022-12-06