函数基础

关于基础部分，可以参考：
https://www.yuque.com/mugpeng/python/dr75i5
https://www.yuque.com/mugpeng/python/wqdvo0

第一个简单的函数

制作一个统计列表中元素出现个数的函数。

利用循环和字典的小特性。

  1. # Define count_entries()
  2. def count_entries(df, col_name):
  3.     """Return a dictionary with counts of 
  4.     occurrences as value for each key."""
  6.     # Initialize an empty dictionary: langs_count
  7.     langs_count = {}
  9.     # Extract column from DataFrame: col
  10.     col = df[col_name]
  12.     # Iterate over lang column in DataFrame
  13.     for entry in col:
  15.         # If the language is in langs_count, add 1
  16.         if entry in langs_count.keys():
  17.             langs_count[entry] += 1
  18.         # Else add the language to langs_count, set the value to 1
  19.         else:
  20.             langs_count[entry] = 1
  22.     # Return the langs_count dictionary
  23.     return langs_count
  25. # Call count_entries(): result
  26. result = count_entries(tweets_df, 'lang')
  28. # Print the result
  29. print(result)
  31. '''
  32. <script.py> output:
  33.     {'en': 97, 'et': 1, 'und': 2}
  34. '''