Loops#

Repeating code using loops#

for <ele> in <sequence>:
    <body>

The loop index variable ele takes on each successive value in the sequence, and the statements in the body of the loop are executed once for each value.
For loops have a limitation – you have to know how many times you are looping – it is a definite loop. The number of iterations is determined when the loop starts. If you do not know how many times you will be looping, use a while loop, which is an indefinite loop that will continue to loop until its condition is no longer true.

while <condition>
    <body>

Loop is controlled using break and continue.

range(start:stop:step) # [start:step:stop)

values = [4, 10, 3, 8, -6]
for i in range(len(values)):
    print(i)

values = [4, 10, 3, 8, -6]
for i in range(len(values)):
    print(i, values[i])

values = [4, 10, 3, 8, -6]
for i in range(len(values)):
    print(i, values[i])

values = [4, 10, 3, 8, -6]
for index, value in enumerate(values):
    print(index, value)

values = [4, 10, 3, 8, -6]
for i in range(len(values)):
    values[i] = values[i] * 2

metals = ['Li', 'Na', 'K']
weights = [6.941, 22.98976928, 39.0983]
for i in range(len(metals)):
    print(metals[i], weights[i])

metals = ['Li', 'Na', 'K']
weights = [6.941, 22.98976928, 39.0983]
for metal, weight in zip(metals, weights):
    print(metal, weight)

elements = [['Li', 'Na', 'K'], ['F', 'Cl', 'Br']]
for inner_list in elements:
    for item in inner_list:
        print(item)

info = [['Isaac Newton', 1643, 1727],
    ['Charles Darwin', 1809, 1882],
    ['Alan Turing', 1912, 1954, 'alan@bletchley.uk']]
for item in info:
    print(len(item))

Do for loop exercises
Do while loop exercises
Do modify loop exercises

File Handling#

with open(filename, 'r') as file:
    for line in file:
        if not line.strip(): # used for skipping empty lines!
            continue
        # do something with line

EAS503

Loops

Contents

Loops#

Repeating code using loops#

File Handling#