Unit 1: Programming and data handling exercises

pythondef is_prime(n):
    if n < 2: return False
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0: return False
    return True

def even_odd(n): return "Even" if n % 2 == 0 else "Odd"

# Alternating series: 1 - 1/2 + 1/3 - ... up to n terms
n = 10
s = sum(((-1) ** (i + 1)) / i for i in range(1, n + 1))
print(round(s, 4))
print(pow(2, 10), 2 ** 10)    # power

pythons = input("String: ")
while True:
    ch = input("1 Frequency  2 Replace  3 Remove  4 Find  5 Exit: ")
    if ch == "1":
        c = input("Char: "); print(s.count(c))
    elif ch == "2":
        old, new = input("Old: "), input("New: "); s = s.replace(old, new); print(s)
    elif ch == "3":
        c = input("Char: "); s = s.replace(c, ""); print(s)
    elif ch == "4":
        sub = input("Find: ")
        print([i for i in range(len(s)) if s.startswith(sub, i)])   # all indices
    elif ch == "5":
        break

pythonimport numpy as np
a = np.full((3, 3), 5); print(a.max(), a.min())
print(np.dot([1, 2, 3], [4, 5, 6]))            # 32
print(np.arange(12).reshape(3, 4))

text = "hello world"
freq = {}
for ch in text.replace(" ", ""):
    freq[ch] = freq.get(ch, 0) + 1
print(freq)

t = (4, 7, 10, 3, 8)
evens = tuple(x for x in t if x % 2 == 0)
print(t[:2], t[2:], evens, t + (1, 2), max(t), min(t))

pythonwith open("in.txt") as src, open("out.txt", "w") as dst:
    for i, line in enumerate(src):
        if i % 2 == 0: dst.write(line)          # copy alternate lines

try:
    print(10 / int(input()))
except ZeroDivisionError:
    print("Division by zero!")

class DuplicateError(Exception): pass
nums = [3, 5, 3]
if len(nums) != len(set(nums)):
    raise DuplicateError("Duplicate values found")

pythonimport matplotlib.pyplot as plt, numpy as np
months = ["Jan", "Feb", "Mar", "Apr"]; profit = [20, 35, 30, 45]
plt.plot(months, profit, marker="o"); plt.title("Monthly profit"); plt.show()
x = np.linspace(-3, 3, 100)
plt.plot(x, x ** 2, label="polynomial"); plt.plot(x, np.exp(x), label="exponential")
plt.legend(); plt.show()