Python control flow

 #control flow

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# 1. if / elif / else

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x = 10

if x > 0:

print("positive")

elif x == 0:

print("zero")

else:

print("negative")

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# 2. for loop

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for i in range(5):

print(f"i={i}", end=" ")

print()

# iterate over a list

for item in ["a", "b", "c"]:

print(item)

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# 3. while loop

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count = 0

while count < 3:

print(f"count={count}",end=" ")

count += 1

print()

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# 4. break, continue, pass

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for n in range(10):

if n == 3:

continue # skip 3

if n == 6:

break # stop at 6

print(n)

for _ in range(5):

pass # placeholder, does nothing

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# 5. for / while with else

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print()

for i in range(3):

print(i)

else:

print("loop finished without break")

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# 6. match / case (structural pattern matching, Python 3.10+)

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command = "quit"

match command:

case "quit":

print("quitting")

case "go" | "move":

print("moving")

case _:

print("unknown command")

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# 7. try / except / else / finally

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try:

result = 10 / 0

except ZeroDivisionError as e:

print(f"caught: {e}")

else:

print("no exception")

finally:

print("always runs")

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# 8. with statement (context manager)

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with open("/dev/null", "w") as f:

f.write("hello") # file is auto-closed after the block

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# 9. comprehensions (inline control flow)

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squares = [x**2 for x in range(5)]

print(squares)

evens = [x for x in range(10) if x % 2 == 0]

print(evens)

square_map = {x: x**2 for x in range(5)}

print(square_map)

unique_even = {x for x in [1, 2, 2, 3, 4] if x % 2 == 0}

gen = (x**2 for x in range(5)) # generator expression

print(gen)

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# 10. ternary (conditional expression)

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label = "even" if x % 2 == 0 else "odd"