Re-defined variable from outer scope PYL-W0621
Anti-pattern
Major
4 months ago
—
4 months old
Redefining name 'data' from outer scope (line 19)
5 def __init__(self, spark):
6 self.spark = spark
7
8 def process_data(self, data): 9 # Process the data using Spark Structured Streaming
10 # For example, calculate the average value of the data
11 df = self.spark.createDataFrame(data, ["value"])Redefining name 'spark' from outer scope (line 17)
2from pyspark.sql.functions import col, avg
3
4class SparkStructuredStreamingProcessor:
5 def __init__(self, spark): 6 self.spark = spark
7
8 def process_data(self, data):Redefining name 'data' from outer scope (line 17)
4 def __init__(self, sc):
5 self.sc = sc
6
7 def process_data(self, data): 8 # Process the data using Spark Streaming
9 # For example, calculate the average value of the data
10 stream = self.sc.parallelize(data)Redefining name 'sc' from outer scope (line 15)
1from pyspark.streaming import StreamingContext
2
3class SparkStreamingProcessor:
4 def __init__(self, sc): 5 self.sc = sc
6
7 def process_data(self, data):Redefining name 'data' from outer scope (line 20)
5 def __init__(self, buffer_size=1000):
6 self.buffer = deque(maxlen=buffer_size)
7
8 def process_data(self, data): 9 # Process the data in real-time
10 # For example, calculate the average value of the data
11 self.buffer.append(data)
Description
The local variable name hides the variable defined in the outer scope, making it inaccessible and might confuse.
Bad practice
filename = 'myfile.txt'
def read_file(filename): # This shadows the global `filename`
with open(filename) as file:
return file.readlines()
Preferred:
FILENAME = 'myfile.txt' # renamed global to UPPER_CASE as convention
def read_file(filename):
with open(filename) as file:
return file.readlines()
Bad practice
Another usual suspect of this is when you use the same parameter name inside a function as the global variable you are using. For example:
def run_app(app):
# This `app` shadows the global app...
app.run()
if __name__ == '__main__':
app = MyApp() # This is a global variable!
run_app(app)
Preferred:
To avoid this re-defining of a global, consider not defining app as a global, but inside a main() function instead:
def run_app(app):
# There is no longer a global `app` variable.
app.run()
def main():
app = MyApp()
run_app(app)
if __name__ == '__main__':
main()