Why is String Concatenation using str.join() Faster Than the = Operator in Python?

Exploring the Speed Gap between String Concatenation and str.join()

In Python, string concatenation can be achieved using the = operator or the str.join() method. This question explores the performance difference between these two approaches.

Method 1: String Concatenation using = Operator

<code class="python">def method1():
  out_str = ''
  for num in range(loop_count):
    out_str += 'num'
  return out_str</code>

Method 4: String Concatenation using str.join()

<code class="python">def method4():
  str_list = []
  for num in range(loop_count):
    str_list.append('num')
  return ''.join(str_list)</code>

Performance Comparison

Benchmarking tests reveal that string join (method 4) is significantly faster than concatenation using the = operator (method 1). This is because strings are immutable in Python. Each concatenation operation requires the creation of a new string object, leading to substantial performance overhead.

Conclusion

For efficient string concatenation in Python, it is highly recommended to use the str.join() method instead of the = operator. This optimization can significantly improve performance, especially for large amounts of string manipulation.

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