Controls and Functions

less = [] greater = [] for x in [1, 2, 3, 4, 8, 6]: if x < 3: less.append(x) else: greater.append(x) print(("less = ", less, "greater = ", greater ))

Variables and Argument Passing

When assigning a variable (or name) in Python, you are creating a reference to the object shown on the righthand side of the equals sign. Consider list of integers.

a = [1, 2, 3] a

b = a b

// In some lanuages, the SSIGNMENT OF B WILL CAUSE [1,2,3] to be copied. In Python, a and b actually now refer to the same object, the origional list [1,2,3]

Conditionals

x = 2 if x < 0: print("It is a negative")

if int(x) < 0: print("It is a negative") elif int(x) == 0: print("equal to 0") elif 0 < int(x) < 5: print("Positive and smaller than 5") else: print("Positive and larger or equal 5")

Loops

squence = [1, 2, 0, 4, 5, 6, 8, 1] total = 0 for value in squence: total += value print(total)

sequence2 = [1, 2, None, 4, None, 5] total = 0 for value in sequence2: if value is None: continue total += value print(total)

sequence3 = [1,2,0,4,5,6,2,1] total_until_5 = 0 for value in sequence3: if value == 5: break total_until_5 += value print(total_until_5)

While Loop

x = 256 total = 0 while x > 0: print(x) if total > 500: break total += x print(total) x //= 2

Range

seq = [10, 20, 30, 40] for i in range(len(seq)): print("element %d: %d" %(i, seq[i]))

enumerate

It's common when iterating over a sequence to want to keep track of the index of the current item.

# enumarate functions l1 = ["eat", "sleep,", "repeat"] # creating enumerate objects obj1 = enumerate(l1) print("Return type:", type(obj1)) print(list(enumerate(l1)))

sorted

The sorted function returns a new sorted list from the elements of any sequence

list = [7, 1, 5, 3, 6, 19, 14, 11] sorted(list)

list

zip

zip "pairs" up the elements of a number of lists, tuples, or other sequences to create a list of tuples.

seq1 = ["Un", "Dos", "Tres"] seq2 = ["one", "two", "three"] zipped = zip(seq1, seq2) list(zipped)

seq3 = [False, True] list(zip(seq1, seq2, seq3))

for index, (a, b) in enumerate(zip(seq1, seq2)): print(f"{index}: {a}, {b}")

reversed

reversed iterates over the elements of a sequence in a reverse order

list(reversed(range(10)))

Lambda Function

Python has support for so-called anonymous functions, which are a way of writing functions consisting of a single statement, the. result of which is the return value. They are defined with the lambda keyword, which has no meaning other than "we are declaring an anonymous function"

def apply_to_list(some_list, f): return [f(x) for x in some_list] ints = [2, 4, 6, 8, 1, 3, 5] apply_to_list(ints, lambda x: x ** 2)

Files and OS

To open a file for reading or writing, use the built-in open functions with either a relative or absolute file path and an optional file encoding.

! wget "https://www.gutenberg.org/files/76/76-0.txt" -O adventures.txt ! ( head -10 adventures.txt) > adventures10.txt

f = open("adventures10.txt", encoding="utf-8") for line in f: print(line)

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