Chapter 5 Control Flow

5.0.1 Looping

5.0.2 Looping Extra

1. for-else

for i in range(5):
    break
else:
    print('else runs cus break didnt run')

In a for-else block, if break runs in the for loop, else doesn’t run if break doesn’t run in the for loop, else will run

2. break vs continue

break stops the entire loop immediately when L=‘C’, break happens, and the entire loop stops.

LETTERS = ['A', 'B', 'C', 'D', 'E']

for L in LETTERS:
  if L == 'C':
    break
  print(L)

## A
## B

continue skips to the next iteration, without stopping the entire loop

LETTERS = ['A', 'B', 'C', 'D', 'E']

for L in LETTERS:
  if L == 'C':
    continue
  print(L)

## A
## B
## D
## E

when L='C', continue executes, and the iteration for L='C' is skipped.

Instead we skip over to the next iteration immediately, where L='D'

Note that continue doesn’t stop the entire loop like break

3. enumerate & zip

enumerate() allows us to generate both index and element at the same time when iterating through a list (or similar iterable).

LETTERS = ['A', 'B', 'C', 'D', 'E']

for i,L in enumerate(LETTERS):
    print(i, L)

## 0 A
## 1 B
## 2 C
## 3 D
## 4 E

zip() allows us to iterate through 2 or more lists (or iterables) at once.

names = ['Adam', 'Eve', 'Joe']
ages = [25,35,18]

for name, age in zip(names, ages):
    print(name, age)

## Adam 25
## Eve 35
## Joe 18