Change over time

df = pd.DataFrame({
    "month": ["Jan", "Feb", "Mar", "Apr"] * 2,
    "mm": [48, 55, 92, 150, 22, 18, 40, 80],
    "city": ["Nairobi"] * 4 + ["Mombasa"] * 4,
})
nairobi = df[df["city"] == "Nairobi"]
plt.plot(nairobi["month"], nairobi["mm"], marker="o")
plt.title("Nairobi rainfall")
plt.ylabel("mm")
plt.show()

df = pd.DataFrame({
    "month": ["Jan", "Feb", "Mar", "Apr"] * 2,
    "mm": [48, 55, 92, 150, 22, 18, 40, 80],
    "city": ["Nairobi"] * 4 + ["Mombasa"] * 4,
})
for city in ["Nairobi", "Mombasa"]:
    sub = df[df["city"] == city]
    plt.plot(sub["month"], sub["mm"], marker="o", label=city)
plt.legend()
plt.title("Two cities")
plt.ylabel("mm")
plt.show()

months = ["Jan", "Feb", "Mar", "Apr"]
plt.bar(months, [48, 55, 92, 150])
plt.title("Bars can show time, but a line reads as change")
plt.show()

df = pd.DataFrame({
    "month": ["Jan", "Feb", "Mar", "Apr"] * 2,
    "mm": [48, 55, 92, 150, 22, 18, 40, 80],
    "city": ["Nairobi"] * 4 + ["Mombasa"] * 4,
})
print(df.groupby("city")["mm"].sum())