String concatenation in loop causes production risks
Note : the rule is restricted to expression with litteral string. Variable string need semantic to be detected.
employee_table = '<table>' for last_name, first_name in employee_list: employee_table += '<tr><td>%s, %s</td></tr>' % (last_name, first_name) employee_table += '</table>'
items = ['<table>'] for last_name, first_name in employee_list: items.append('<tr><td>%s, %s</td></tr>' % (last_name, first_name)) items.append('</table>') employee_table = ''.join(items)
Why you should care
Avoid using the + and += operators to accumulate a string within a loop. Since strings are immutable, this creates unnecessary temporary objects and results in quadratic rather than linear running time. Instead, add each substring to a list and ”.join the list after the loop terminates (or, write each substring to a io.BytesIO buffer).
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