Analyzing the U.S. Births dataset in Python
If you want to do data-analysis in Python, you should learn about numpy and pandas. The former implements efficient numeric calculations (on whole arrays). The latter uses numpy and introduces a DataFrame, which is a bit like a table that can be manipulated in many ways. You can sort it by some column(s), you can transform them and you can even group them by some column(s) and perform operations on the groups (which is what you want to do here).

Your current code boils down to very few lines with pandas:

import pandas as pd

df = pd.read_csv("us_birth_statistics.csv", skipinitialspace=True)
birth_per_month = df.groupby("month").births.sum()
birth_per_weekday = df.groupby("day_of_week").births.sum()

print(birth_per_month)
print()
print(birth_per_weekday)

#month
#1    48311
#Name: births, dtype: int64

#day_of_week
#1    10142
#2    11248
#3    11053
#6     8096
#7     7772
#Name: births, dtype: int64