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fig = plt.gcf() # or by other means, like plt.subplots
figsize = fig.get_size_inches()
fig.set_size_inches(figsize * 1.5) # scale current size by 1.5
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import matplotlib.pyplot as plt
fig, ax = plt.subplots(figsize=(10,10)) # Sample figsize in inches
sns.heatmap(df1.iloc[:, 1:6:], annot=True, linewidths=.5, ax=ax)