Control Flow — Decisions, Loops & Comprehensions

if / elif / else

Same idea as PHP, cleaner spelling. The keyword is elif (not else if or elseif), and every branch ends in a colon with an indented body.

score = 82
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "F"
print(grade)   # B

The comparison operators are the familiar set: == != < > <= >=. Combine conditions with the words and, or, not — not the && || ! symbols you'd use in PHP. Python deliberately spells them out for readability.

if revenue > target and not on_holiday:
    print("Push for the stretch goal")

🐘 PHP: Three swaps to remember: elseif → elif, && → and, || → or. And there's no switch in older Python; you use elif chains (or match in 3.10+, which you'll rarely need at first).

Truthiness — what counts as "empty"

Python treats a handful of values as "falsy": False, 0, 0.0, "" (empty string), [] (empty list), {} (empty dict), and None. Everything else is "truthy." This lets you write the very natural-reading idiom:

orders = []
if not orders:
    print("No orders to process")   # this runs — empty list is falsy

🐘 PHP: Very close to PHP's truthiness, with one big mercy: "0" (the string zero) is truthy in Python, whereas in PHP it's falsy and bites people constantly. And there's no loose == type-juggling madness — 0 == "0" is just False in Python.

The for loop — iterate over things directly

Python's for loops over the items of a collection, not over a counter. You almost never write for (i = 0; i < n; i++).

regions = ["North", "South", "East", "West"]
for region in regions:
    print(f"Processing {region}")

Need the index too? Wrap the collection in enumerate():

for i, region in enumerate(regions):
    print(f"{i}: {region}")

And when you genuinely need a counter (say, "do this 5 times"), use range():

for n in range(5):       # 0,1,2,3,4
    print(n)
for n in range(1, 6):    # 1,2,3,4,5  (start, stop — stop is excluded)
    print(n)

🐘 PHP: foreach ($regions as $region) becomes for region in regions:. PHP's foreach ($arr as $k => $v) has two Python equivalents depending on the shape: enumerate() for list index+value, and .items() for dict key+value (next chapter).

while, break, continue

while repeats until its condition goes false. break bails out of the loop entirely; continue skips to the next iteration. Identical meanings to PHP.

attempts = 0
while attempts < 3:
    attempts += 1
    if attempts == 2:
        continue          # skip the rest of this pass
    print(f"Attempt {attempts}")

The comprehension — your new favourite tool

This is the one to internalise. A list comprehension builds a new list by transforming (and optionally filtering) an existing one, in a single expressive line. It's the Pythonic replacement for "make an empty list, loop, append."

prices = [10, 25, 40, 8, 100]

# transform: add 15% tax to every price
with_tax = [p * 1.15 for p in prices]

# filter: keep only the big-ticket items
big = [p for p in prices if p >= 40]

# transform + filter together
discounted_big = [p * 0.9 for p in prices if p >= 40]

Read it left to right as a sentence: "p times 1.15, for each p in prices." Once this clicks, you'll reach for it dozens of times a day — cleaning columns, reshaping records, pulling fields out of data. It's faster than a manual loop and, more importantly, it states intent instead of mechanics.

There's a dict version too, which you'll use to remap data:

names = ["north", "south", "east"]
lookup = {name: len(name) for name in names}
# {'north': 5, 'south': 5, 'east': 4}

🐘 PHP: PHP has no direct equivalent — the closest is array_map() + array_filter(), but those need callbacks and read awkwardly. The comprehension does both jobs in one line you can actually read aloud. This is a genuine quality-of-life upgrade over the PHP way.