Python Conditionals¶
Sometimes you will want to execute certain sections of code based on specific conditions. This is where the conditionals come in. You can use different comparision and logical operators. There include: < > <= >= = !=
Conditions and IF Statements¶
Imagine you're comparing the scores of two gamers in a video game competition:
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score_gamer1 = 280
score_gamer2 = 350
if score_gamer2 > score_gamer1:
print("Gamer 2 has a higher score than Gamer 1")
score_gamer1 = 280
score_gamer2 = 350
if score_gamer2 > score_gamer1:
print("Gamer 2 has a higher score than Gamer 1")
Gamer 2 has a higher score than Gamer 1
ELIF Statements¶
The elif keyword is used for checking multiple conditions sequentially:
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day = "Friday"
if day == "Monday":
print("Start of the work week!")
elif day == "Friday":
print("Weekend is here!")
day = "Friday"
if day == "Monday":
print("Start of the work week!")
elif day == "Friday":
print("Weekend is here!")
Weekend is here!
ELSE Statements¶
The else clause catches anything not addressed by the preceding conditions:
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weather = "sunny"
if weather == "rainy":
print("Don't forget your umbrella!")
else:
print("Enjoy the sunshine!")
weather = "sunny"
if weather == "rainy":
print("Don't forget your umbrella!")
else:
print("Enjoy the sunshine!")
Enjoy the sunshine!
You can also have an else without the elif:
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pet = "cat"
if pet == "dog":
print("Woof woof!")
else:
print("Some pet other than a dog!")
pet = "cat"
if pet == "dog":
print("Woof woof!")
else:
print("Some pet other than a dog!")
Some pet other than a dog!
Using AND in IF Statements¶
The and keyword combines conditional statements:
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temperature = 22
is_raining = True
if temperature > 20 and is_raining:
print("Warm but rainy, you might need a light raincoat.")
temperature = 22
is_raining = True
if temperature > 20 and is_raining:
print("Warm but rainy, you might need a light raincoat.")
Warm but rainy, you might need a light raincoat.
Using OR in IF Statements¶
The or keyword is used when only one of multiple conditions needs to be true:
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snack = "chocolate"
diet_day = False
if snack == "vegetables" or not diet_day:
print("It's okay to eat the snack!")
snack = "chocolate"
diet_day = False
if snack == "vegetables" or not diet_day:
print("It's okay to eat the snack!")
It's okay to eat the snack!
Nested IF Statements¶
Nested if statements are useful for more specific conditions:
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score = 92
if score > 50:
print("Great! You passed the test,")
if score > 90:
print("and you scored an A!")
else:
print("but try for a higher score next time.")
score = 92
if score > 50:
print("Great! You passed the test,")
if score > 90:
print("and you scored an A!")
else:
print("but try for a higher score next time.")
Great! You passed the test, and you scored an A!
pass Statement¶
Sometimes, you might want to define a conditional structure with no action yet:
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mood = "happy"
if mood == "happy":
pass # Placeholder for future code
mood = "happy"
if mood == "happy":
pass # Placeholder for future code