If statement

Programming for Geoscientists Data Science and Machine Learning for Geoscientists

if construct allows to create cases in the code based on conditions:

    if condition:
        # Execute some code if condition is True
    elif condition2:
        # Execute some code only if condition is False and condition2 is True
    else:
        # Execute some code only if both condition and condition2 are False

elif and else are optional blocks. Code inside each block needs to be indented.

Example use

number = 10

if number < 5:
    print("%g is less than 5." % (number))
elif number < 12:
    print("%g is less than 12." % (number))
else:
    print("%g is greater or equal to 12." % (number))
    
# If statements in one line
a = 1 if number == 5 else 0
print(a)

10 is less than 12.
0

Exercises

---

• Flow control: What is the difference between the output of the following code samples:

a = 5

if a < 5:
    print("foo")
elif a == 5:
    print("bar")
else:
    print("boom")

a = 4

if a < 5:
    print("foo")
elif a == 5:
    print("bar")
else:
    print("boom")

a = 4
if a <5:
    print("foo")
elif a == 5:
    print("bar")

print("boom") 

Answer

First: bar

Second: foo

Third: foo boom